TY - JOUR
T1 - Malignant melanoma of anorectal region
T2 - A clinicopathologic study of 61 cases
AU - Tariq, Muhammad Usman
AU - Ud Din, Nasir
AU - Ud Din, Nausheen Feroz
AU - Fatima, Saira
AU - Ahmad, Zubair
N1 - Publisher Copyright:
© 2014 Elsevier Inc. All rights reserved.
PY - 2014/10/1
Y1 - 2014/10/1
N2 - Anorectal malignant melanomas (AMMs) are aggressive neoplasms, which account for less than 1% of all anorectal tumors. Anorectal malignant melanomas are notorious for their diversity of histologic features and mimic a number of other tumors. Aberrant expression of immunohistochemical stains such as cytokeratins and CD117 (c-kit) further increases the risk of misdiagnosis. Aim of our study was to describe the common as well as unusual architectural and cytologic features that create difficulty in diagnosis. We also discussed the role of immunohistochemical stains in diagnosis of AMMs. We retrieved and reviewed 61 cases of anal melanoma diagnosed in our institution between January 2005 and May 2014. Epithelioid cell type was observed in 57 (93.4%) cases, spindle cells in 35 (57.4%) cases, pleomorphic in 12 (19.7%) cases, and lymphoma-like in 2 (3.3%) cases. Cytoplasmic clearing was observed in 16.4% and nuclear pseudoinclusions in 9.8% cases. Twenty-one point three percent cases were completely amelanotic, and 36.1% showed focal melanin pigment. Average mitotic count was 2 mitoses/high-power fields. Nesting pattern was seen in 24.6%, pseudoalveolar pattern in 11.5%, and peritheliomatous/pseudopapillary pattern in 5% cases. Positive expression of vimentin, S-100, HMB-45, and Melan A was seen in 100%, 100%, 94.4%, and 93.3% cases, respectively. Cytokeratins were positive in 9% and CD117 (c-kit) in 20% of cases in which they were performed. In conclusion, AMMs should be considered in the differential of any malignant tumor of anorectal region without obvious glandular and squamoid differentiation. The knowledge of amelanotic nature, unusual histologic features, and aberrant immunohistochemical expression is helpful in avoiding misdiagnosis.
AB - Anorectal malignant melanomas (AMMs) are aggressive neoplasms, which account for less than 1% of all anorectal tumors. Anorectal malignant melanomas are notorious for their diversity of histologic features and mimic a number of other tumors. Aberrant expression of immunohistochemical stains such as cytokeratins and CD117 (c-kit) further increases the risk of misdiagnosis. Aim of our study was to describe the common as well as unusual architectural and cytologic features that create difficulty in diagnosis. We also discussed the role of immunohistochemical stains in diagnosis of AMMs. We retrieved and reviewed 61 cases of anal melanoma diagnosed in our institution between January 2005 and May 2014. Epithelioid cell type was observed in 57 (93.4%) cases, spindle cells in 35 (57.4%) cases, pleomorphic in 12 (19.7%) cases, and lymphoma-like in 2 (3.3%) cases. Cytoplasmic clearing was observed in 16.4% and nuclear pseudoinclusions in 9.8% cases. Twenty-one point three percent cases were completely amelanotic, and 36.1% showed focal melanin pigment. Average mitotic count was 2 mitoses/high-power fields. Nesting pattern was seen in 24.6%, pseudoalveolar pattern in 11.5%, and peritheliomatous/pseudopapillary pattern in 5% cases. Positive expression of vimentin, S-100, HMB-45, and Melan A was seen in 100%, 100%, 94.4%, and 93.3% cases, respectively. Cytokeratins were positive in 9% and CD117 (c-kit) in 20% of cases in which they were performed. In conclusion, AMMs should be considered in the differential of any malignant tumor of anorectal region without obvious glandular and squamoid differentiation. The knowledge of amelanotic nature, unusual histologic features, and aberrant immunohistochemical expression is helpful in avoiding misdiagnosis.
KW - Anorectal
KW - CD117 (c-kit)
KW - HMB-45
KW - Malignant melanoma
KW - Melan-A
KW - Melanin pigment
UR - http://www.scopus.com/inward/record.url?scp=84908255696&partnerID=8YFLogxK
U2 - 10.1016/j.anndiagpath.2014.08.002
DO - 10.1016/j.anndiagpath.2014.08.002
M3 - Article
C2 - 25163722
AN - SCOPUS:84908255696
SN - 1092-9134
VL - 18
SP - 275
EP - 281
JO - Annals of Diagnostic Pathology
JF - Annals of Diagnostic Pathology
IS - 5
ER -