Most osteomalacia-associated mesenchymal tumors are a single histopathologic entity: an analysis of 32 cases and a comprehensive review of the literature.
Oncogenic osteomalacia (OO) is a rare paraneoplastic syndrome of osteomalacia due to phosphate wasting. The phosphaturic mesenchymal tumor (mixed connective tissue variant) (PMTMCT) is an extremely rare, distinctive tumor that is frequently associated with OO. Despite its association with OO, many PMTMCTs go unrecognized because they are erroneously diagnosed as other mesenchymal tumors. Expression of fibroblast growth factor-23 (FGF-23), a recently described protein putatively implicated in renal tubular phosphate loss, has been shown in a small number of mesenchymal tumors with known OO. The clinicopathological features of 32 mesenchymal tumors either with known OO (29) or with features suggestive of PMTMCT (3) were studied. Immunohistochemistry for cytokeratin, S-100, actin, desmin, CD34, and FGF-23 was performed. The patients (13 male, 19 female) ranged from 9 to 80 years in age (median 53 years). A long history of OO was common. The cases had been originally diagnosed as PMTMCT (15), hemangiopericytoma (HPC) (3), osteosarcoma (3), giant cell tumor (2), and other (9). The tumors occurred in a variety of soft tissue (21) and bone sites (11) and ranged from 1.7 to 14 cm. Twenty-four cases were classic PMTMCT with low cellularity, myxoid change, bland spindled cells, distinctive "grungy" calcified matrix, fat, HPC-like vessels, microcysts, hemorrhage, osteoclasts, and an incomplete rim of membranous ossification. Four of these benign-appearing PMTMCTs contained osteoid-like matrix. Three other PMTMCTs were hypercellular and cytologically atypical and were considered malignant. The 3 cases without known OO were histologically identical to the typical PMTMCT. Four cases did not resemble PMTMCT: 2 sinonasal HPC, 1 conventional HPC, and 1 sclerosing osteosarcoma. Three cases expressed actin; all other markers were negative. Expression of FGF-23 was seen in 17 of 21 cases by immunohistochemistry and in 2 of 2 cases by RT-PCR. Follow-up (25 cases, 6-348 months) indicated the following: 21 alive with no evidence of disease and with normal serum chemistry, 4 alive with disease (1 malignant PMTMCT with lung metastases). We conclude that most cases of mesenchymal tumor-associated OO, both in the present series and in the reported literature, are due to PMTMCT. Improved recognition of their histologic spectrum, including the presence of bone or osteoid-like matrix in otherwise typical cases and the existence of malignant forms, should allow distinction from other mesenchymal tumors. Recognition of PMTMCT is critical, as complete resection cures intractable OO. Immunohistochemistry and RT-PCR for FGF-23 confirm the role of this protein in PMTMCT-associated OO.
Folpe
Andrew L
AL
Department of Pathology and Laboratory Medicine, Emory University, Atlanta, GA, USA. afolpe@emory.edu
Fanburg-Smith
Julie C
JC
Billings
Steven D
SD
Bisceglia
Michele
M
Bertoni
Franco
F
Cho
Justin Y
JY
Econs
Michael J
MJ
Inwards
Carrie Y
CY
Jan de Beur
Suzanne M
SM
Mentzel
Thomas
T
Montgomery
Elizabeth
E
Michal
Michal
M
Miettinen
Markku
M
Mills
Stacey E
SE
Reith
John D
JD
O'Connell
John X
JX
Rosenberg
Andrew E
AE
Rubin
Brian P
BP
Sweet
Donald E
DE
Vinh
Tuyethoa N
TN
Wold
Lester E
LE
Wehrli
Brett M
BM
White
Kenneth E
KE
Zaino
Richard J
RJ
Weiss
Sharon W
SW
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis*; D001859:Bone Neoplasms / Q000150:complications / Q000473:pathology; D002648:Child; D003937:Diagnosis, Differential; D005260:Female; D000089703:Fibroblast Growth Factor-23; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008637:Mesenchymoma / Q000150:complications / Q000473:pathology*; D008875:Middle Aged; D010018:Osteomalacia / Q000150:complications*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012983:Soft Tissue Neoplasms / Q000150:complications / Q000473:pathology
D014408:Biomarkers, Tumor; C000717427:FGF23 protein, human; D000089703:Fibroblast Growth Factor-23