Epithelioid Rhabdomyosarcoma: Clinicopathologic  Analysis of 16 Cases of a Morphologically Distinct Variant   of Rhabdomyosarcoma                                  Am J Surg Pathol  Volume 35, Number 10, October 2011
讨论：1.上皮样RMS有这种分型？
      2.上皮样RMS的好发年龄？部位？容易转移的部位？
      3.上皮样RMS与胚胎性，腺泡型，多形性RMS在预后上有何不同？
      4.坏死在这种肿瘤中的意义？与预后是否有关系？
      5.结合HE,在鉴别诊断中我们要多加注意。

Abstract: Rhabdomyosarcoma (RMS), which affects mainly
pediatric patients, is currently classified into 3 major categories:
embryonal, alveolar, and pleomorphic. We have identified a
distinct variant of RMS that is characterized by epithelioid
morphology, reminiscent of poorly differentiated carcinoma or
melanoma, for which we propose the designation “epithelioid
RMS.” We examined the clinicopathologic features of 16 such
cases, which were received in consultation between 1991 and 2009.
Ten patients were men, and 5 were women (gender was unknown in
1 case), with a median age of 70.5 years (range 14 to 78). Primary
anatomic sites were upper extremity (4), lower extremity (2), head
and neck (3), trunk (3), hypopharynx (1), and left atrium (1). Two
patients presented with nodal metastases (neck and mediastinal)
with unknown primary sites. Of the tumors in somatic locations, 10
were intramuscular, and 2 were subcutaneous. Tumor size ranged
from 3 to 8.5cm; the tumors had nodular fleshy cut surfaces,
grossly appreciable necrosis, and infiltrative edges.Microscopically,
tumors showed sheet-like growth of uniformly sized epithelioid cells
with abundant amphophilic-to-eosinophilic cytoplasm, large vesicular
nuclei, and frequently prominent nucleoli. Necrosis and
infiltration into adjacent structures (such as skeletal muscle or fat)
were present in all cases, and mitotic counts were high (median
count 23 per 10 high-power fields) with frequent atypical forms. By
immunohistochemistry, all tumors showed diffuse desmin expression,
and myf-4 immunostaining was diffuse to multifocally
positive. S100-protein was absent in all cases. Cytokeratin was
negative in 12 cases and very focally positive in 4 cases. Clinical
follow-up information was available for 11 cases (median duration
10 mo). Most patients underwent surgical resection with chemotherapy
and/or radiation (none with RMS-specific protocols).
Two patients had multiple recurrences, and 2 patients developed
satellite nodules near the primary lesion. Six patients had regional
lymph node metastases, and 6 patients developed distant metastases
most commonly to the lung. So far, 7 patients have died of
disease, 5 within 1 year and 2 within 5 years. Epithelioid RMS is a
novel morphologically distinct variant of RMS that closely mimics
carcinoma or melanoma. It primarily affects older patients, with a
male predilection. The clinical course as determined thus far is
aggressive.