26 October 2006 – Case of the Week #63
The next case will be sent on Wednesday, November 8, 2006.
These cases can also be accessed by clicking on the Case of the Week button on the left hand side of our Home Page at www.PathologyOutlines.com. This email is sent only to those who subscribe in writing or by email. To view the images or references, you must click on the links in blue.
To subscribe or unsubscribe, email [email protected], indicating subscribe or unsubscribe to Case of the Week. We do not sell, share or use your email address for any other purpose. We also maintain two other email lists: to receive a biweekly update of new jobs added to our Jobs pages, and to receive a monthly update of changes made to the website. You must subscribe or unsubscribe separately to these email lists.
How can you find detailed pathology information in 15 seconds or less? Use our free online textbook. From the Home page at www.PathologyOutlines.com, click on the appropriate chapter, then on the topic in the Table of Contents, and you will be directed to clinical information, gross and microscopic images, immunohistochemistry and other stain results, references and other pertinent information. This is a good way to quickly refresh your memory on any entity you have not seen in a while.
We thank Dr. Sharon Bihlmeyer, University of Vermont, Burlington, Vermont (USA), for contributing this case. We invite you to contribute a Case of the Week by sending an email to [email protected] with microscopic images (any size, we will shrink if necessary) in JPG or GIF format, a short clinical history, your diagnosis and any other images (gross, immunostains, EM, etc.) that may be helpful or interesting. We will write the discussion (unless you want to), list you as the contributor, and send you a check for $35 (US) for your time after we send out the case. Please only send cases with a definitive diagnosis.
Case of the Week #63
A 53 year old man presented with a 4 month history of a protuberant and painful left anterior pretribial mass. Eleven years previously, he had an excision of a similar mass in the same location. Metabolic laboratory studies were within normal limits, including a phosphorus level of 4.4 mg/dL. An excisional biopsy was performed.
What is your diagnosis?
(scroll down to continue)
Phosphaturic Mesenchymal Tumor
Phosphaturic Mesenchymal tumor is extremely rare. It affects women slightly more commonly than men, with a median age 53 years, but a wide range of 9-80 years.
This tumor often produce oncogenic osteomalacia, characterized by low serum phosphate, reduced tubular reabsorption of phosphate and a low or inappropriately normal 1,25 dihydroxy Vitamin D. In children, it may cause rickets (Pediatr Dev Pathol 2000;3:61).
These tumors are usually benign, and complete excision typically causes dramatic reversal of the endocrine signs and symptoms (AJSP 1989;13:588)
Grossly, the tumors may be up to 14 cm, and arise in soft tissue and bone. They are hypocellular, composed of bland spindled cells with small nuclei and indistinct nucleoli, as well as osteoclast-like giant cells. The stroma exhibits myxoid change, a distinctive “grungy” calcified matrix, metaplastic bone and fat. There may be hemangiopericytoma-like vessels, microcysts and hemorrhage. The tumors are infiltrative, but there is typically no/rare mitotic activity, and no atypia. Cases are considered malignant if they have nuclear atypia, high cellularity and 5+ mitotic figures/10 HPF.
Immunohistochemistry is not routinely used. However, the tumor cells are immunoreactive for fibroblast growth factor-23 (AJSP 2004;28:1) and dentin matrix protein 1 (Mod Path 2004;17:573), which are thought to mediate their metabolic effects, and may be useful in difficult cases.
The differential diagnosis includes other mesenchymal tumors, such as hemangiopericytoma, osteosarcoma and giant cell tumor.
This case showed a normal phosphorus, which is not typical, and some mitotic figures. However, the diagnosis was confirmed by Dr. Christopher Fletcher at Harvard.
Nat Pernick, M.D., President
30100 Telegraph Road, Suite 404
Bingham Farms, Michigan (USA) 48025
Email: [email protected]