Photo Quiz: A 55-Year-Old-Man with Rectal Bleeding and a Rectal Mass

A 55-year-old man with a history of tobacco use presented with a 5-day history of diarrhea and rectal bleeding. This was associated with intermittent low-grade fever and weight loss that he was not able to quantify. There was no family history of malignancy. He had traveled frequently within South East Asia, and his last travel had been 6 months prior to this presentation.

Physical examination revealed a medium-built male who was hemodynamically stable, with a temperature of 38°C on presentation. His cardiovascular, respiratory, and abdominal examination was normal, with no organomegaly. Digital rectal examination showed a craggy irregular nonobstructing mass at the 11- to 1-o’clock position, 6 cm from the anal verge, without contact bleeding.

His laboratory investigations revealed a white blood cell count of 11.5 × 10⁹/liter (neutrophils, 63%; lymphocytes, 24.5%; eosinophils, 3%), normocytic normochromic anemia (12.5 g/dl), and a platelet count of 373 × 10⁹/liter. C-reactive protein level was 75 mg/liter. Renal function and transaminases were normal. One set of blood cultures (BD Bactec Plus Aerobic/F and Plus Anaerobic/F culture vials) incubated on the BD Bactec FX (Becton, Dickinson Biosciences) automated blood culture system detected no bacterial growth in all bottles after 5 days of incubation. Contrast-enhanced computed tomography of the thorax, abdomen, and pelvis revealed irregular wall thickening in the mid-rectum, in keeping with rectal malignancy. There were enlarged superior hemorrhoidal and inferior mesenteric lymph nodes, which were suspicious for nodal disease.

Colonoscopy was performed and showed ulceration at the transverse colon and a circumferential low rectal tumor, 5 cm from the anal verge, associated with contact bleeding (Fig. 1A). Multiple biopsy specimens from the lesion were taken. Histology photomicrographs from hematoxylin and eosin (H&E) and periodic acid-Schiff-diastase (PAS-D) stains are shown (Fig. 1B, C, and D).

FIG 1.

(A) Circumferential low rectal tumor 5 cm from the anal verge seen during colonoscopy. (B and C) Hematoxylin and eosin (H&E) stain at magnifications of ×100 (B) and ×400 (C) shows necrosis with fibrinoid material, scattered inflammatory cells, and abundant objects. (D) Periodic acid-Schiff-diastase (PAS-D) stain at a magnification of ×200, highlighting the objects.

What is the diagnosis?