of Week Home
11 April 2012 - Case of the Week #238
All cases are archived on our website. To view them sorted by number, diagnosis or category, visit our Home Page and click on the Case of the Week button on the left hand side. To subscribe or unsubscribe to the Case of the Week or our other email lists, click here.
Thanks to Dr. Tihana Dzombeta, University of Zagreb, Croatia, for contributing this case. To contribute a Case of the Week, follow the guidelines on our Case of the Week page.
(1) We are constantly looking for Reviewers for each of our 7,000 topics, which we plan to update every 1-2 years. In particular, we are looking for reviewers of Soft Tissue Tumors and various Stains. Visit our newly updated Instructions for Reviewers page for more information.
(2) The Table of Contents of our Stains chapter now includes all 360 stains / biomarkers described in the chapter. The CD Markers chapter contains an additional 260 markers. We update these pages regularly, but let us know of any new markers we should include or other changes we should make.
(3) Our Feature Page for the month highlights Lab Accrediation, Education and CME, and includes A2LA, ARUP Laboratories and Clinical and Laboratory Standards Institute (CLSI) . Also check out our new monthly Mystery Image, on the right side of the Home Page.
(4) The Kidney tumor - cysts, children, adult benign chapter has now been updated, based on reviews by Mandolin Ziadie, M.D.
Case of the Week #238
An 81 year old man had a painless tumor of his left great toe, which was excised. Macroscopically, the tumor was well-circumscribed, measured 4 x 3 x 2.5 cm and was located in the subcutis.
What is your diagnosis?
Symplastic glomus tumor
The tumor was encapsulated and composed of solid sheets of cells separated by vessels of varying size and lined with normal appearing, CD34+ endothelium. The neoplastic cells showed pronounced nuclear pleomorphism, hyperchromasia and occasional intranuclear inclusions. Mitotic activity was sparse, up to 2 mitoses/50 HPF, but the Ki-67 proliferative rate was about 25%. There were no atypical mitotic figures, but areas of necrosis were present. Tumor cells were diffusely immunoreactive for smooth muscle actin (SMA), vimentin and desmin.
Left to right: CD34, Ki-67
Left to right: smooth muscle actin, vimentin, desmin
Glomus tumors are neoplasms differentiating toward specialized cells found in the glomus body, a structure involved in thermoregulation (Arch Pathol Lab Med 2008;132:1448, Int J Surg Pathol 2011;19:499). Symplastic glomus tumors, first described in 1995 as epithelioid glomus tumors (Hum Pathol 1995;26:1022) have marked nuclear atypia but no other criteria for malignancy. Less than 25 cases have been reported in the English literature (Am J Dermatopathol 2009;31:71).
The differential diagnosis includes malignant glomus tumor, which has metastatic potential (AJ Cutan Pathol 2009;36:1099). A comprehensive study defined malignant glomus tumors as having a deep location and size >2 cm, or atypical mitotic figures, or moderate to high nuclear grade and 5 or more mitotic figures/50 HPF (Am J Surg Pathol 2001;25:1).
Symplastic glomus tumors have benign behavior, and excision is curative.
Nat Pernick, M.D., President
and Liz Parker, B.A., Associate Medical Editor
30100 Telegraph Road, Suite 408
Bingham Farms, Michigan (USA) 48025
Alternate email: NatPernick@gmail.com