Rectal Metastasis from Breast Cancer: A Case Report and Review of Literature

Abstract

Introduction

Metastatic spread of breast cancer to the gastrointestinal (GI) tract is very uncommon (<1% of all metastases), but it is disproportionately higher in invasive lobular carcinoma (ILC) compared to invasive ductal carcinoma. Its presentation can mimic primary rectal malignancy, often leading to delayed diagnosis.

Case Presentation

We describe a 40-year-old woman with metastatic, hormone receptor-positive classic ILC who developed rectal obstruction 2 years after her breast cancer diagnosis. Initial colonoscopy with superficial biopsies was negative. One year later, pelvic magnetic resonance imaging (MRI) demonstrated smooth, concentric thickening of the rectal wall; repeat biopsies confirmed metastatic lobular carcinoma.

Conclusion

This case illustrates the diagnostic challenges posed by rectal metastasis from ILC, especially negative superficial rectal biopsies. Endoscopic and radiologic features often mimic primary rectal pathology, underscoring the importance of deep biopsy and imaging in establishing the diagnosis. New lower-GI symptoms in any breast-cancer survivor, especially one with ILC, should prompt pelvic MRI and deep tissue sampling to exclude metastatic disease if superficial biopsies are negative.

Introduction

Breast cancer is the most frequently diagnosed cancer in women worldwide [1]. While bone, liver, lung, and brain are its canonical metastatic destinations [2], gastrointestinal (GI) involvement is documented in <1% of cases [3]. Among reported cases of GI metastases from breast cancer, around half involved the large bowel (cecum, colon, sigmoid, and rectum), and the other half the small bowel (duodenum, jejunum, and ileum). Metastatic involvement of the stomach or anus is exceedingly rare, each occurring in fewer than 1% of cases [4]. Invasive lobular carcinoma (ILC) accounts for roughly 10% of primary breast tumors, yet it contributes 60–80% of breast-to-GI metastases [4, 5]. Loss of E-cadherin in ILC disrupts intercellular adhesion, allowing diffuse single-file (“Indian-file”) infiltration along serosal and submucosal planes and explaining its predilection for hollow viscera, peritoneum, and retroperitoneum [3, 6, 7]. Although rectal deposits represent the minority of GI metastases with approximately 7% [8], they hold significant clinical relevance as their endoscopic and radiologic features frequently mimic those of primary rectal adenocarcinoma, leading to diagnostic delay.

Case Report/Case Presentation

We present a 40-year-old BRCA2-positive woman, known for irritable bowel syndrome and a remote appendectomy. She was diagnosed in March 2023 with stage IV classic-type ILC of the left breast (ER 90%, PR 3%, HER2-negative), with synchronous bone and liver metastases. She received sequential endocrine therapy with a CDK4/6 inhibitor, olaparib, and a HER2-targeting antibody-drug conjugate trial.

In April 2024, after treatment for Clostridioides difficile colitis, she developed abdominal cramps and diarrhea. Computed tomography of the abdomen-pelvis revealed marked circumferential rectal thickening involving the entire rectum. A colonoscopy was performed, which revealed a rigid, narrowed rectum. However, superficial mucosal biopsies demonstrated only erosions and reactive changes, with no evidence of malignancy. She was given a prednisone taper, which relieved her symptoms.

In May 2025, she re-presented with tenesmus, intermittent diarrhea, and one episode of hematochezia. Digital rectal examination revealed a firm stenosis. Magnetic resonance imaging (MRI) of the pelvis demonstrated an 11-cm segment of smooth, concentric mural thickening with “linitis plastica” appearance and mesorectal stranding (shown in Fig. 1). Repeat colonoscopy revealed erythematous friable stenosis between 5 and 20 cm from the anal verge (shown in Fig. 2), and superficial biopsies confirmed metastatic lobular breast carcinoma (ER-/PR-, GATA-3 positive, E-cadherin negative) (shown in Fig. 3). Systemic restaging showed new peritoneal carcinomatosis and progression of the known bone metastases; the patient opted for comfort-focused care and passed away in June 2025.

Fig. 1.

Rectal MRI demonstrating diffuse smooth circumferential thickening of the rectum reaching up to 1.1 cm with mural stratification manifested by marked mucosal and muscularis hyperenhancement and late enhancing, intermediate T2 submucosal layer associated with extensive stranding of the mesorectal fascia.

Fig. 2.

a, b Endoscopic images from May 2025 demonstrating an erythematous, friable stenosis located 5–20 cm from the anal verge.

Fig. 3.

Histologic sections of metastatic lobular breast carcinoma involving the colon. a Hematoxylin and eosin-stained section demonstrating single-file infiltration of discohesive malignant cells within the colonic wall, characteristic of lobular carcinoma morphology. b Immunohistochemical staining for GATA3 shows diffuse and strong nuclear positivity in the infiltrating tumor cells, confirming the breast origin of the metastasis. Normal colonic epithelium is negative for GATA3, serving as an internal negative control.

The CARE Checklist has been completed by the authors for this case report, attached as online supplementary material (for all online suppl. material, see https://doi.org/10.1159/000550604).

Discussion

Given the rare nature of rectal metastasis from breast cancer, a review of the available literature was performed to catalogue the most reported clinical features, key endoscopic and radiologic findings, as well as therapeutic strategies. A summary of the findings can be found in Table 1.

Table 1.

Overview of reported cases of rectal metastasis from breast cancer in the literature

Author	Time between cancer and GI symptoms	Concomitant metastasesa	Clinical presentation	Endoscopy findings	Biopsy findings	Imaging findings	Treatment of rectal metastasis
Wang et al. [9] (2024)	Synchronous	Axillary and supraclavicular lymph nodes	Constipation, abdominal pain	Colonoscopy: Mucosal congestion, swelling, and thickening	N/A	CT: thickening of the lower rectum and ascending colon + lymph nodes in the axilla	Laparoscopic radical resection of rectum
Age: 67F
Type of cancer: NA
Saeed et al. [10] (2024)	Synchronous	Mesorectal and iliac lymph nodes, bones (spine)	Constipation, abdominal pain, nausea, anorexia, weight loss	Colonoscopy: malignant appearing apple-core lesion at proximal rectum with severe stenosis, 10 cm from anal verge	Signet ring cells, CK7+ CK20 neg CDX2	CT: circumferential rectal lesion seen on colonoscopy, 17.5 mm thickness, 7 cm length	Palliative chemo
Age: 52F							Laparoscopic loop colostomy
Type of cancer: ILC, ER+ PR+ HER2, signet ring cell type							Endocrine therapy
Mazza et al. [11] (2022)	Synchronous	Lymph nodes	Constipation, reduced stool caliber, abdominal pain, tenesmus	Colonoscopy: severe congestion of the rectal mucosa and stenosis of the lumen	From colonoscopy: Nonspecific inflammatory infiltrate	CT: concentric severe thickening of rectal wall resulting in lumen narrowing, perirectal fat stranding	Neoadjuvant chemotherapy
Age: 69F				EUS: marked thickening of rectal wall up to 16 mm, predominance of submucosa and muscularis propria, maintained stratification, poor vascularization at color Doppler, multiple lymph nodes in mesorectum	EUS-guided FNB: poorly diff adenocarcinoma of extraintestinal origin, ER-PR-HER2-, suspicious for invasive lobular breast carcinoma	MRI: confirmed rectal thickening, enhancement of rectal mucosa and anal canal. Target sign visible on T2-weigheted and DWI.	Planned for surgery
Type of cancer: ILC, triple negative
Hoang et al. [12] (2022)	11 years	Lung	Hematochezia, abdominal pain	Colonoscopy: infiltrating rectal lesion occupying ½ of rectal circumference	Core bx: breast carcinoma ER+PR++HER2neg	CT: mild thickening of rectal wall and no suspected lymph nodes	Chemotherapy
Age: 49F
Type of cancer: IDC, triple neg
Algethami et al. [13] (2022)	4 years	N/A	Abdominal distention, abdominal pain, weight loss	Colonoscopy: 8 cm congested mass, 4 cm from anal verge, bleed easily, circumferential involvement	Lamina propria infiltrated with 2 atypical cells, and adenocarcinoma metastatic from breast (ER++ HER2+)	N/A	N/A
Age: 47F
Type of cancer: ILC ER++ PR+ HER2-
Ban et al. [14] (2021)	5 years	Bone (acetabulum)	Constipation, hematochezia, hypogastric pain	Colonoscopy: circumferential stricture in lower rectum at 3 cm from anal verge, smooth and red surface	No malignancy	PET-CT: uptake at the distal rectum + acetabulum	Colostomy
Age: 36F							Chemotherapy
Type of cancer: IDC pT1N1M0 grade 2 ER+PR+ HER2-							Radiotherapy
							Endocrine therapy
Fontes et al. [15] (2021)	Synchronous	Axillary and mesorectal lymph nodes, bones (shoulder, mandible, spine, ankle)	Obstipation, hematochezia, weight loss	No endoscopy reported	poorly diff carcinoma, IHC compatible with breast tumor (CK7 and GATA3 positive, ER-. CDX2 neg)	CT: Concentric parietal thickening of rectum with increased lymph nodes in perirectal fat	Colostomy
Age: 43F						MRI: 10.6 cm lesion with irregular and circumferential contours in the middle and lower rectum/anal canal, at 0.7 cm from the anal border, mesorectal lymphadenopathy
Type of cancer: ILC, ER+ PR-
Vande Berg et al. [16] (2021)	Synchronous	No other metastasis reported	Tenesmus, dyschezia, fecal incontinence	Rectosigmoidoscopy: erythematous mucosa up to 10 cm from anal verge without visible endoluminal lesion	bx: CK7 positive so adenocarcinoma, CDX2 neg so not GI origin, ER+PR+	Rectal MRI: 1 cm thickening of rectal wall over 10 cm with no perirectal adenopathy	Neoadjuvant chemotherapy
Age: 61F						CT: thickening of rectal wall without metastases	Protectomy with mesorectal excision
Type of cancer: ILC						PET: slightly increased activity in the rectum and left axillary adenopathy mot likely 2/2 recent breast biopsy
Cherian et al. [17] (2017)	19 years	No other metastasis reported	Abdominal pain, anal pain, change in bowel habits, weight loss	Colonoscopy: 5 rectal sessile polyps	Metastatic lobular breast carcinoma	CT: No rectal findings	Endocrine therapy
Age: 79F				2nd colonoscopy weeks later: stenosis of distal sigmoid colon, edematous mucosa
Type of cancer: IDC Grade 2
Lau et al. [4] (2017)	11 years	No other metastasis reported	Increased stool frequency, mucous, reduced caliber	Colonoscopy: circumferential lesion distal rectum causing luminal narrowing	N/A	CT: 9 cm segment of diffuse circumferential wall thickening mid rectum to anal canal with luminal narrowing, marked perirectal fat stranding, no abdominopelvic adenopathy, no hepatic mets	​
Age: 61F						MRI: diffuse concentric mural thickening of rectum and anal canal, wall thickening involving submucosa and muscularis propria, sparing mucosa
Type of cancer: ILC T1N0M0						T2-weigheted: laminated architecture of wall preserved, extramural component of tumor very hypodense
Guzman-Calderon et al. [18] (2017)	3 years	No other metastasis reported	Painless rectal bleeding	Colonoscopy: hyperemic and nodular lesion of rectal mucosae suggestive of neoplastic infiltrate with rectal structure, located 8–12 cm from anal verge	Initial bx: No malignancy	CT and MRI: mucosal thickening involving the whole rectum with involvement of perirectal fat	N/A
Age: 65F					Repeat bx: rectal metastatic lesion of invasive lobular breast cancer, ER+ PR+ HER2-
Type of cancer: ILC ER+PR+ HER2 neg
Venturini et al. [19] (2016)	Synchronous	Bone (T12, pelvis)	Abdominal pain, tenesmus	Rectosigmoidoscopy: rectal circumferential lumen narrowing and wall thickening from 3 to 11 cm above dentate line, normal macroscopic mucosa	Superficial bx: no malignancy	CT and MRI: circumferential rectal mass with normal boundary of the muscularis propria and small lymph nodes in the perirectal fat	Ultralow anterior rectal resection
Age: 69F						T2-weighted MRI: rectal wall thickening with sparing of the mucosal layer
Type of cancer: ILC pT1b
Osaku et al. [20] (2015)	Synchronous	Peritoneum	Constipation	N/A	Superficial bx (from endoscopy): no malignancy	Barium enema: rectosigmoid stenosis, no irregularities of mucosa	Chemotherapy
Age: 68F					Surgical biopsy: ILC metastasis	CT: thickening of rectosigmoid wall in the stenotic region	Endocrine therapy
Type of cancer: ILC
Xue et al. [21] (2015)	7 years	No other metastasis reported	Asymptomatic	Colonoscopy: negative	N/A	CT: 3 × 4cm heterogenous mass in the pelvic cavity	Laparoscopic resection of mesorectal mass
Age: 68F
Type of cancer: IDC pT2N0M0 ER+ PR- HER2-
Ng et al. [22] (2015)	5 years	Adnexa, peritoneum	Asymptomatic	Colonoscopy: stricture in rectum 16 cm from anal verge	Metastatic lobular carcinoma ER+ HER2-	CT: stricture in the rectum at the recto-sigmoid junction	Chemotherapy
Age: 56F
Type of cancer: ILC ER+ HER2- and IDC grade 1
Matsuda et al. [23] (2012)	24 years	No other metastasis reported	Constipation	Endoscopy: 2 circumferential strictures in ascending colon and stricture	Poorly differentiated adenocarcinoma of the rectum	PET/CT: 2 areas of increased uptake in the rectum	Chemotherapy and radiotherapy
Age: 62F							Proctectomy with low anterior resection
Type of cancer: ILC
Ambroggi et al. [24] (2012)	Synchronous	No other metastasis reported	Hematochezia	Colonoscopy: substenosis 7 cm fron anal verge	Metastasis from breast cancer, moderately differentiated, partial aspects of signet ring cells, ER++PR+HER2neg	No rectal findings	Chemotherapy
Age: 40F							Radiotherapy
Type of cancer: IDC with signet cells ER++, PR+, HER2 -							Endocrine therapy
Elsaify et al. [25] (2012)	19 years	No other metastasis reported	Altered bowel habits	Colonoscopy: thigh rectal stricture, 10 cm from anal verge	​	CT/MRI: diffuse mural thickening of rectal wall	Rectal resection
Age: 61F							Adjuvant chemo
Type of cancer: ILC							Endocrine therapy
Nair [26] (2012)	7 years	Axillary nodes	Change in bowel habits, abdominal pain, increased bowel frequency	Colonoscopy: circumferential ulcerative growth, starting about 3 cm from the anal verge and extending up to 5 cm	Adenocarcinoma of apocrine appearance infiltrating between intact bowel crypts, CK7 +, CK20 neg, CEA neg	N/A	Loop colostomy
Age: 57F							Radiotherapy
Type of cancer: IDC Grade 3 ER/PR-HER2+
Carcoforo et al. [27] (2012)	30 years	Diffuse carcinomatosis of abdomen	Abdominal pain, nausea, emesis, intestinal obstruction	Colonoscopy: stricture 15 cm from anal verge	From endoscopy: No malignancy	CT: 8 cm pelvic mas	Endoscopic stent
Age: 73F					Surgical bx: metastatic ILC		Left colectomy with diverting end colostomy
Type of cancer: ILC
Rajan et al. [28] (2012)	9 years	Bone (tibia)	Change in bowel habits, rectal bleeding	Colonoscopy: fungating tumor 10 cm from anal verge	Bx: poorly differentiated invasive adenocarcinoma CK7+, ER+, CEA neg, CK20 neg -> metastatic breast origin	MRI: locally advanced tumor with involvement of mesorectal fascial margins with possible involvement of peritoneum locally	Low anterior resection with end colostomy
Age: 60F
Type of cancer: IDC ER+
Gerova et al. [29] (2012)	5 years	Stomach, liver	Abdominal pain, change in bowel habits, tenesmus, intermittent blood in stools, fatigue, weight loss	Colonoscopy: rigid and stenotic rectum, bulky hyperemic irregular soft bleeding lesions, 3–10 cm from anal verge, compatible with Crohn’s	Endoscopy: nonspecific colitis	N/A	Palliative care
Age: 56F				EUS: neoplastic lesion 4–10 cm from anal verge, infiltrative zones were with heterogenous structure and transversial size 1.5/2 cm	Deep rectal bx from EUS: infiltration in the mucosa, submucosa and muscularis mucosa by atypical cells with predominantly round nucleus and dispersed chromatin, epithelium immunophenotype
Type of cancer: ILC PR+
Eljabu et al. [30] (2011)	4 months	Small bowel	Diarrhea, rectal bleeding	Sigmoidoscopy: narrowed lumen, firm swollen mucosa upper rectum	Bx: metastatic ILD, CK7 +, ER +	CT: left hydronephrosis form compression of rectal metastasis on ureter	Palliative care
Age: 70F
Type of cancer: ILC ER+ PR+ HER2-
Arrangioz et al. [31] (2011)	Synchronous	Gastric, liver, lung, peritoneum	Intermittent abdominal pain, colicky in nature, diarrhea, 10Lbs weight loss	Colonoscopy: circumferential obstructing rectal mass, required use of pediatric colonoscope to advance beyond lesion, lesion measured 4 cm starting 3 cm from anal verge	Bx: poorly diff carcinoma ER/PR positive	CT 1: negative	N/A
Age: 70F						CT 2: circumferential thickening of rectum, from rectosigmoid junction to anus
Type of cancer: ILC ER+ PR- HER2-
Amin et al. [32] (2011)	17 years	Axillary lymph nodes	Change in bowel habits, loose stools, fecal urgency	Colonoscopy: circumferential smooth structuring lesion in rectum 10 cm from anal verge	bx: inconclusive	CT and MRI abdomen: mucosal thickening of the whole rectum, preservation of mural structures, no suggestion of malignancy	Hartmann’s resection
Age: 61F							Endocrine therapy
Type of cancer: ILC ER+ PR+
Saranovic et al. [33] (2011)	6 years	Peritoneum, omentum	prolonged constipation, early satiety, weight loss	Sigmoidoscopy: thickening and rigidity of rectal wall, stenosis of the lumen 10 cm above anal verge	bx: diffuse infiltration of tumor cells along the rectal wall, some presenting “signet-ring cell” type, CK7, CA 15-3, ER positive	MRI: extension of tumor tissue through muscle layer and obliteration of the interface between muscle and perirectal fat	Colo-ano pull through anastomosis and subsequent closing colostomy
Age: 47F						PET: high uptake in rectal wall (SUV 9.8)	Endocrine therapy
Type of cancer: ILC ER+ PR+
Efthimiadis et al. [34] (2011)	5 years	No other metastasis reported	Severe constipation, tenesmus, straining, recurrent lower abdominal pain subsiding after defecation, fatigue	Anoscopy: mass at the lower rectum, 2 cm from anal verge, hindered passage of endoscope, smooth surface, grossly granular, swollen, red, suggesting submucosal tumor	N/A	CT and MRI abdomen: rectal mass, thickness of rectal wall, prestenotic dilatation	Abdominoperineal excision with transection of the back wall of the vagina
Age: 74F
Type of cancer: ILC
Balja et al. [35] (2010)	7 years	Pericolic lymph nodes	Constipation	Endoscopy: no endoscopic findings	bx = single-file stands of infiltrating small tumor cells, loosely dispersed throughout lamina propria, signet-ring cells, CK7 +, ER+, PR neg	N/A	Abdominoperineal resection
Age: 83F
Type of cancer: ILC ER+ PR+
López cheracias et al. [36] (2009)	15 years	Bone (spine)	Back pain	Colonoscopy: thickening of mucosa with stenosis of lumen 7 cm from anal verge	Bx: poorly diff adenocarcinoma with signet ring cells infiltrating mucosa with a linitis appearance (negative ER PR)	CT abdomen: pelvic mass arising from rectosigmoidal junction	Double J for hydronephrosis, no other therapy as patient passed away 2 months later
Age: 67F
Type of cancer: ILC
Ikeda et al. [37] (2008)	4 years	Liver	Anemia, bloody stools	Colonoscopy: edema, yellowish-white polypoid lesion in the rectal mucosa	bx: diffuse tissue infiltration by tumor cells, ER+	Barium enema: rectal stenosis	Endocrine therapy
Age: 64m						CT abdomen: eccentric thickening of rectal wall
Type of cancer: IDC ER+
Gleeson et al. [38] (2008)	N/A	N/A	Constipation	Colonoscopy: circumferential rectal wall thickening at 7 cm from anal verge	EUS- FNA: Positive for malignancy; adenocarcinoma, favoring metastatic lobular carcinoma	N/A	N/A
Age: 51F				EUS: Diffuse circumferential thickening of the rectal wall involving all layers
Type of cancer: ILC
Yanagisawa et al. [39] (2007)	Synchronous	No other metastasis reported	Anal pain during defecation	Colonoscopy: edema, redness of rectal mucosa	bx: negative, no malignancy	CT abdomen and barium enema: severe stenosis and eccentric wall thickening with luminal narrowing of rectum	Chemotherapy
Age: 47F					Surgical bx: CK7, ER and PR positive, CEA negative		Hormonotherapy
Type of cancer: IDC ER+ PR+
Franceschini et al. [40] (2006)	15 years	Ovaries, bladder, vagina, ureter, peritoneum	Diffuse abdominal pain, constipation, tenesmus, sporadic rectal bleeding	Sigmoidoscopy: diffuse thickening of anterior wall of rectum, mild stenosis beginning 7 cm above anal verge, without evidence of endoluminal masses, anterior wall was hyperemic mucosa and easily bleeding	Bx: extensive infiltration of scarcely cohesive neoplastic cells, ‘Indian file’ neoplastic growth pattern (IHC: ER + PR + CK7 +, CK20 – CA125 – CDX2 -)	CT abdomen: pelvic cavity was almost completely occupied by neoplastic tissue which infiltrated the rectal wall, causing marked stenosis, enlarged lymph nodes in perirectal fat	Chemotherapy
Age: 67F							Hormonotherapy
Type of cancer: ILC ER+ PR+
Laoutliev et al. [41] (2005)	N/A	Omentum	Obstructive symptoms, tenesmus, incontinence	Colonoscopy: stricture 1–15 cm from anal verge, lumen 10 mm, oedematous endothelium	N/A	PET: increased uptake in the rectum, consistent with malignancy	Rectum extirpation
Age: 57F				EUS: universal wall thickening without pararectal involvement		MRI: universal thickening of rectum, intact muscularis propria layer, mesorectum fibrotic changes	Radiotherapy
Type of cancer: ILC ER+							Endocrine therapy
Bailey et al. [42] (2002)	Synchronous	Meningeal	Change in bowel habits	Colonoscopy: stricture at 5 cm	Bx: metastatic adenocarcinoma from ILC	N/A	Chemotherapy
Age: 36F							Endocrine therapy
Type of cancer: ILC
Bar-Zohar et al. [43] (2001)	6 years	No other metastasis reported	Lower abdominal pain, tenesmus, change bowel habits	Colonoscopy: bulky hyperemic irregular lesion narrowing rectal lumen 5–9cm from anal verge	Bx: nonspecific colitis	CT abdomen: normal	Radiotherapy
Age: 68F					TRU-CUT bx of rectum: malignant ductal cells infiltracting rectal wall, CA15-3 +, ER+ CK7+ CEA neg, PR neg		Chemotherapy
Type of cancer: IDC ER+ PR-
Bamias et al. [44] (2001)	9 years	Peritoneum, bladder	Constipation and tenesmus	Sigmoidoscopy 1: diffuse inflammatory area of lower rectum	Bx 1: NEGATIVE	CT abdomen: thickness of rectal wall	Chemotherapy (no improvement of symptoms)
Age: 74F				Sigmoidoscopy 2: ulcerated area with stenosis of lumen 7 cm above anal verge	Bx 2: infiltration from malignant cells of signet ring type = metastatic breast carcinoma		Sigmoid colostomy
Type of cancer: ILC ER+ PR+
Cervi et al. [45] (2001)	8 years	Peritoneal and lymph nodes	Tenesmus, incontinence, blood in stool	Sigmoidoscopy: stenosis of rectum, rigidity and stiffness of wall 5–16 cm from anal verge, solitary ulcer	Deep biopsies: infiltration of epithelial carcinoma compatible with lobular breast primary	N/A	Abdominoperineal resection
Age: 59F
Type of cancer: ILC ER+ PR+
Nieboer et al. [46] (2000)	Synchronous	Axillary lymph nodes	Irregular bowel movements	Colonoscopy: stenosis of distal rectum with congestive mucosal folds	Deep bx: ILC metastasis	N/A	Chemotherapy
Age: 55F				EUS: thickening of muscularis propria and rectal wall – linitis plastica
Type of cancer: ILC ER+ PR+
Shimonov et al. [47] (2000)	12 years	Lymph nodes	Abdominal distention	Colonoscopy and EUS: Rectal mass	Bx: poorly differentiated carcinoma	N/A	Abdominoperineal resection
Age: 72F
Type of cancer: ILC
Dumontier et al. [48] (1997) Patient A	2 years	N/A	N/A	EUS: Rectal wall thickening 15 mm with perirectal fat infiltration	N/A	N/A	N/A
Age: 52F
Type of cancer: N/A
Dumontier et al. [48] (1997) Patient B	3 years	N/A	N/A	EUS: 8 mm rectal wall thickening with perirectal fat infiltration	N/A	N/A	N/A
Age: 76F
Type of cancer: N/A
Dumontier et al. [48] (1997) Patient C	3 years	N/A	N/A	EUS: 20 mm rectal wall thickening, no perirectal fat infiltration	N/A	N/A	N/A
Age: 60F
Type of cancer: N/A
Clavien et al. [49] (1990)	Synchronous	N/A	Diarrhea	N/A	N/A	CT, barium enema, US listed in table but no findings	Endocrine therapy
Age: 82F
Type of cancer: ILC ER+ HER2-
Balthazar et al. [50] (1979)	N/A	N/A	Distention, constipation, tenesmus	Could not be done due to rectal narrowing	N/A	Barium enema: colonic obstruction secondary to rectal narrowing over 9 cm	N/A
Age: 65F
Type of cancer: N/A
Asch et al. [51] (1968) Patient A	6.5 years	N/A	Constipation, rectal mass	N/A	N/A	N/A	Colostomy
Age: 58F
Type of cancer: N/A
Asch et al. [51] (1968) Patient B	1.5 years	N/A	Nausea, obstipation, rectal mass	N/A	N/A	Barium enema: colonic dilatation	Colostomy
Age: 75F
Type of cancer: N/A

^aAt the time of rectal metastasis diagnosis.

The time between the diagnosis of breast cancer and the onset of GI symptoms is very variable. Of the cases reviewed, one-third of patients presented with GI symptoms from rectal metastasis before receiving a diagnosis of breast cancer (synchronous presentation). The majority of cases had an asynchronous presentation of GI symptoms, ranging from 4 months to up to 30 years after initial diagnosis of breast cancer, which is consistent with intervals reported in previous reports [4, 24, 52]. In the present case, rectal metastasis was diagnosed only 2 years after the initial ILC diagnosis, likely due to the cancer’s aggressive and rapidly disseminating nature.

Among the cases that reported on additional metastatic sites, half demonstrated disseminated disease, while the other half showed only local lymph node involvement or no other metastases. As illustrated by the case reported above, rectal metastasis may signal widespread disease; nevertheless, the literature shows that many patients present without systemic dissemination.

Common symptoms include altered bowel habits, obstruction, hematochezia, or abdominal pain, which closely mimic primary rectal malignancy and lead to diagnostic challenges [52]. The tendency of rectal metastasis to diffusely infiltrate the wall, leading to its thickening and rigidity, explains the commonly reported clinical presentations [44, 53]. In the present case, abdominal pain and hematochezia were reported, along with diarrhea, which is less usual for rectal metastasis.

As ILC is characterized by a diffuse infiltrative growth pattern [33, 54], the most commonly reported endoscopic finding is circumferential thickening and rigidity, which can again mimic primary rectal linitis plastica [24, 55]. Because lobular tumor nests lodge first in submucosa or muscularis propria [52, 55], the initial superficial endoscopic mucosal biopsies were falsely negative in approximately one-fourth of the cases from the review. In half of those cases, a repeat superficial biopsy later in time or a deeper biopsy/endoscopic ultrasound (EUS)-guided fine-needle aspiration revealed the diagnosis. In the present case, the positive repeat superficial biopsy 1 year later suggests that rectal involvement progressed from the serosa and submucosa inward, eventually infiltrating the mucosal layer.

Pelvic MRI and EUS are particularly informative, frequently demonstrating a smooth concentric rectal thickening with relative mucosal sparing [19], features atypical of primary rectal adenocarcinoma [8, 55]. Computed tomography and positron emission tomography were also performed regularly in the cases reviewed, but failed to provide findings that could distinguish the lesion from primary rectal carcinoma. The present case aligned with those findings.

Treatment is individualized. Surgery was the preferred approach in half of the cases reviewed, often complemented with noninvasive methods such as neoadjuvant or adjuvant chemotherapy, radiotherapy, and endocrine therapy. In McLemore’s cohort, median overall survival after diagnosis of GI metastasis was 28 months; systemic endocrine therapy or chemotherapy conferred a survival benefit, whereas palliative surgery improved symptoms without significantly extending life [5]. Decisions should balance disease extent, performance status, and patient preferences.

To conclude, classic-type ILC exhibits a well-documented predilection for the GI tract. Clinicians should maintain a high index of suspicion when breast cancer survivors, especially those with ILC, develop new lower-GI symptoms. Negative superficial rectal biopsies do not rule out metastatic disease; pelvic MRI coupled with deep or EUS-guided biopsy is essential for accurate diagnosis and timely, multidisciplinary management [9–18, 20–23, 25–32, 34–43, 45–51].

Statement of Ethics

Written informed consent was obtained from the patient for publication of the details of their medical case and any accompanying images prior to their passing away. Ethical approval is not required for this study in accordance with local or national guidelines.

Conflict of Interest Statement

All the authors have no conflicts of interest to declare.

Funding Sources

This study was not supported by any sponsor or funder.

Author Contributions

F.A.C. and H.H.D. obtained written consent, collected the clinical information on the case, and performed the literature review. F.A.C., H.H.D., J.A., and C.R.M.K. participated in the redaction of the original draft of the manuscript and figures. T.B. read and approved the final version of the manuscript. F.A.C., H.H.D., and T.B. were responsible for the decision to submit the manuscript.

Funding Statement

This study was not supported by any sponsor or funder.

Data Availability Statement

All data generated or analyzed during this study are included in this published article. No additional datasets were generated. Further inquiries can be directed to the corresponding author.