PMC6599445_01
(A) Computed tomography findings of the abdominopelvis. Several enlarged lymph nodes are noted at the gastrosplenic area. (B) 18F-fluorodeoxyglucose positron emission tomography identified mild uptake (standardized uptake value max 2.8) in the gastrosplenic area. (C) Gross examination showed oval solid mass measuring 2.2 x 1.3 cm.
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At the abdominopelvic computed tomography scan made in December 2015, several enlarged LNs were found in the gastrosplenic area (Fig. 1A). 18F-fluorodeoxyglucose positron emission tomography identified mild uptake (standardized uptake value max 2.8) in the gastrosplenic area (Fig. 1B), which was highly suspicious of rectal cancer relapse. The cut surface showed homogeneously solid and brown color (Fig. 1C).
(A) Representative scan view of hematoxylin and eosin staining of the resected specimen (taken at 0.4x objective). (B) Epithelioid cells were arranged in a nested or alveolus-like architecture with surrounding branching thin-walled vascular spaces (taken at 10x objective) (C) The individual epithelioid cells show clear to eosinophilic granular cytoplasm with prominent nucleus and mitoses was also found (taken at 40x objective).
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Microscopic findings showed a thick fibrous capsule in the periphery of the nodule with some LN features (Fig. 2A). Epithelioid cells occupied most of the LN, being arranged in a nested or alveolus-like architecture supported by branching thin-walled vascular spaces and/or delicate collagenous stroma (Fig. 2B). Individual epithelioid cells had clear to granular eosinophilic cytoplasm (Fig. 2C).
Representative imaging for immunohistochemical staining. Tumor cells showed (A) strong cytoplasmic expression for HMB45 and (B) strong nuclear expression for TFE3. (C) In contrast, tumor cells showed no expression for Melan-A (all images were taken with a 20x objective lens).
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In immunohistochemical studies, HMB45 and TFE3 were strongly and diffusely expressed (Fig. 3A and B). In contrast, Melan-A (Fig. 3C), smooth muscle actin, CK, and S100 were not expressed.