A case of a benign tumor with marked melanin pigmentation localized within the inferior vena cava

Abstract

A 65-year-old woman with no significant medical history was incidentally found to have a well-circumscribed lesion in the inferior vena cava on computed tomography. Despite unremarkable clinical findings and inconclusive preoperative assessments, she underwent surgical resection for diagnostic and therapeutic purposes. Complete excision was achieved, and histopathological analysis revealed a benign tumor with abundant melanin pigmentation. No recurrence was observed during 1 year of follow-up without adjuvant therapy. This case highlights the importance of surgical intervention for both diagnosis and treatment in managing tumors of the inferior vena cava.

Tumors of the inferior vena cava (IVC) are rare. Benign primary tumors include myxomas and leiomyomas, and leiomyosarcoma is the most frequently reported malignant tumor.^1,2 Although pigmented tumors such as melanoma have been reported in the IVC, they are typically of metastatic origin.3, 4, 5 Herein, we present a rare case of a benign, melanin-pigmented tumor localized to the IVC, discovered incidentally. Histopathological examination revealed features distinct from those of previously documented IVC tumors, suggesting a unique pathological entity. Written informed consent was obtained from the patient for publication of her case details.

Case report

A 65-year-old woman with no significant medical history and no prior treatment for malignancy presented with acute abdominal pain. Computed tomography (CT) was performed to evaluate the cause and revealed acute appendicitis, for which she underwent a laparoscopic appendectomy. Incidentally, the same CT scan also demonstrated an 18 × 10 mm mass within the IVC, located inferior to the renal vein. After the appendectomy, the patient's abdominal symptoms resolved, and no signs of chronic venous insufficiency, including lower extremity edema, were observed. Additionally, there were no physical findings suggestive of malignancy, such as weight loss. A noncontrast CT demonstrated a well-circumscribed, hyperdense, ellipsoidal mass (Fig 1, A and B). Contrast-enhanced CT showed no enhancement in the arterial phase (Fig 1, C) and only minimal uptake in the delayed phase (Fig 1, D). Magnetic resonance imaging revealed a hyperintense signal on T1-weighted images, whereas the lesion was inconspicuous on T2-weighted images. Ultrasound examination confirmed the presence of an intracaval mass with minimal internal vascularity. Positron emission tomography demonstrated fluorodeoxyglucose uptake within the IVC lesion, with a maximum standardized uptake value of 3.9 (Fig 1, E), and no other suspicious findings. Whole-body imaging identified an adrenal adenoma, but revealed no evidence of additional malignancy. Upper and lower gastrointestinal endoscopy revealed no abnormalities. Routine laboratory testing, including D-dimer levels, was unremarkable (D-dimer <0.5 μg/mL). In the absence of a definitive preoperative diagnosis, and at the patient's request for both diagnostic clarification and therapeutic intervention, surgical resection of the IVC tumor was performed.

Fig 1.

(A) Preoperative noncontrast coronal computed tomography (CT) scan illustrating a tumor within the inferior vena cava (IVC), located inferior to the renal vein (white arrow). (B) Magnified view of (A). (C) Arterial-phase contrast-enhanced CT scan showing minimal enhancement of the tumor. (D) Venous-phase contrast-enhanced CT scan demonstrating slight intralesional enhancement. (E) Positron emission tomography (PET) imaging confirming fluorodeoxyglucose (FDG) uptake within the IVC tumor.

A midline laparotomy was performed, and the IVC was exposed after mobilization of the right colon and duodenum (Fig 2, A). A palpable mass was identified within the IVC, with a blackened area on its left wall corresponding with the presumed origin of the tumor (Fig 2, B). No evidence of invasion into adjacent structures was observed. Intraoperative ultrasound examination confirmed the high mobility of the mass (Fig 2, C, and the Supplementary Video, online only). Complete resection was achieved with a minimum surgical margin of 1 cm, and vascular reconstruction was performed using a 16-mm ring-reinforced Gore-Tex graft (W. L. Gore & Associates) (Fig 2, D). The resected specimen was a well-circumscribed, soft, black tumor, with the darkened area of the IVC wall corresponding with its attachment site (Fig 2, E). The postoperative course was uneventful, and the patient was discharged on postoperative day 10.

Fig 2.

(A) Surgically exposed inferior vena cava (IVC) (cranial side oriented upward). (B) The tumor's root embedded in the left IVC wall, showing characteristic black pigmentation. (C) Intraoperative ultrasonography showing the tumor firmly attached at its base but highly mobile. (D) Vascular reconstruction was performed using an expanded polytetrafluoroethylene (ePTFE) graft. (E) Gross specimen of the excised tumor, appearing as a soft, black mass.

Histopathological examination revealed no thrombotic components on hematoxylin and eosin staining. The lesion was composed entirely of pigmented cells proliferating predominantly within the lumen of the IVC and infiltrating the adventitial layer (Fig 3, A). Hematoxylin and eosin staining demonstrated densely proliferative cells containing abundant blackish-brown pigment (Fig 3, B), which was identified as melanin based on negative staining with Berlin blue and blue staining with Giemsa. Immunohistochemically, the tumor was positive for HMB45, a widely used marker for malignant melanoma (Fig 3, C), but negative for SOX10, a highly specific and sensitive marker that has been recently adopted for melanoma diagnosis (Fig 3, D). The Ki-67 labeling index was very low (<5%), and the lesion was considered benign.

Fig 3.

(A) Hematoxylin and eosin (HE) staining showing a tumor composed entirely of pigmented neoplastic cells mainly located in IVC and infiltrating the adventitia (stain: HE; original magnification ×20). (B) HE staining demonstrated densely proliferating cells containing abundant blackish-brown pigment (stain: HE; original magnification ×200). (C) Immunohistochemistry for HMB45 with Giemsa stain. The tumor cells show positive light brown staining for HMB45, and the pigment is stained blackish blue with Giemsa (stain: Giemsa; original magnification ×400). (D) Immunohistochemistry for SOX10 with Giemsa stain. The tumor cells are negative for SOX10, and the pigment is stained blackish blue with Giemsa (stain: Giemsa; original magnification ×Giemsa).

Given the pigmented nature of the tumor, a comprehensive dermatologic and mucosal examination was performed, including evaluation of the skin, vulva, vagina, oral cavity, and bulbar conjunctiva, all of which revealed no abnormalities. The patient has remained under close surveillance without adjuvant therapy, with no evidence of recurrence observed during 1 year of follow-up. This case represents a rare instance of a benign, melanin-pigmented tumor localized within the IVC.

Discussion

Tumors of the IVC, whether primary or secondary, are rare. Among benign primary tumors, myxomas and leiomyomas have been reported; leiomyosarcoma is the most common malignant primary tumor.^1,2 Secondary involvement of the IVC, most frequently from renal cell carcinoma via direct invasion or tumor thrombus, is more commonly observed than primary malignant lesions.^1,2

IVC myxomas are exceedingly rare and typically arise near the junction of the IVC and right atrium, the Eustachian valve, or the suprahepatic segment.6, 7, 8 These typical sites of origin differ from that of the present case. Vascular smooth muscle tumors originating in the IVC are also rare and include both benign and malignant entities. Although primary IVC leiomyomas have been reported,⁹ most smooth muscle tumors are classified as intravenous leiomyomatosis, a variant of uterine leiomyoma that extends into venous structures and may occasionally reach the cardiac chambers.¹⁰ Despite their benign histological features, intravenous leiomyomatosis lesions may exhibit clinically aggressive behavior, suggesting malignant potential.¹¹ A rare subtype, intravenous lipoleiomyomatosis, has also been described.¹² Among malignant smooth muscle tumors, leiomyosarcoma is the most frequently reported primary vascular malignancy of the IVC.¹³

Other rare IVC tumors include epithelioid hemangioendothelioma, a neoplasm of borderline malignancy,¹⁴ and benign lesions such as lipomas¹⁵ and lymphatic cysts.¹⁶ In addition to renal cell carcinoma, other secondary tumors involving the IVC have been documented, including mixed epithelial and stromal tumors of the kidney,¹⁷ renal angiomyolipoma,¹⁸ and solitary fibrous tumors.¹⁹

Pigmented tumors of the IVC are extremely rare. To date, no reports have described a nevus arising within the IVC. Melanoma can involve the IVC, but most cases represent metastasis from a known primary site, direct invasion from adjacent organs, or tumor thrombus from adrenal or renal primaries.3, 4, 5 Melanoma of unknown primary involving the right atrium has been reported,²⁰ typically with extensive invasion, but there are no known cases of melanoma of unknown primary localized solely within the IVC.

Taken together, the present case represents an exceedingly rare example of a benign, melanin-pigmented tumor localized within the IVC, with no detectable primary lesion. We consulted several pathologists regarding the diagnosis, but no definitive pathological diagnosis was obtained. Immunohistochemically, the tumor was positive for HMB45, raising the possibility of a melanocytic nevus or a perivascular epithelioid cell tumor.²¹ However, the histological features were not consistent with either diagnosis. As far as we could determine from the available literature, there are no reports of such tumors arising from the vessel wall. Its histological features, immunoprofile, and lack of recurrence over 1 year of follow-up support a benign biological behavior. However, given the rarity and diagnostic complexity of such pigmented vascular tumors, careful pathological evaluation and long-term surveillance are warranted.

Conclusions

We present a rare case of a benign, melanin-pigmented tumor localized within the IVC. Surgical resection proved to be a valuable approach for both diagnostic clarification and therapeutic management.

Funding

None.

Disclosures

None.

Appendix (online only)

Supplementary Video

Intraoperative ultrasonography showing the inferior vena cava (IVC) tumor moving within the vessel, resembling a basketball being dribbled. The left side of the image corresponds with the right atrium, and the right side with the lower extremities.