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Year : 2019  |  Volume : 62  |  Issue : 2  |  Page : 360-361
Catechism (Quiz 4)

Department of Surgical Pathology, Tata Memorial Hospital, Mumbai, Maharashtra, India

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Date of Web Publication10-Apr-2019

How to cite this article:
Rekhi B. Catechism (Quiz 4). Indian J Pathol Microbiol 2019;62:360-1

How to cite this URL:
Rekhi B. Catechism (Quiz 4). Indian J Pathol Microbiol [serial online] 2019 [cited 2022 Aug 16];62:360-1. Available from: https://www.ijpmonline.org/text.asp?2019/62/2/360/255803

   Clinical History Top

A 32-year-old lady underwent a hysteroscopic myomectomy, elsewhere, for a suspected fibroid. Paraffin blocks of the excised tumor were submitted to us for review.

Microscopic findings

Hematoxylin and eosin-stained sections showed a tumor composed of polygonal-shaped cells, arranged in cords and in small clusters containing moderate amount of eosinophilic-to-vacuolated cytoplasm and round nuclei. Interspersed were areas of hyalinization. Individual tumor cells displayed moderate degree of nuclear atypia [Figure 1]a,[Figure 1]b,[Figure 1]c. On immunohistochemistry, tumor cells were diffusely positive for pan cytokeratin (AE1/AE3) [Figure 1]d.
Figure 1: (a) Tumor composed of polygonal-shaped cells, arranged in cords and in small clusters. with cytoplasmic clearing, at places. [H and E, × 200] (b). Cells containing moderate amount of eosinophilic to focally vacuolated cytoplasm and round to oval nuclei [H and E, × 400]. (c). Interspersed areas of eosinophilic material. Individual tumor cells displayed moderate degree of nuclear atypia. [H and E, × 400]. (d). By immunohistochemistry, tumor cells showing diffuse positivity for pan cytokeratin (AE1/AE3). [Diaminobenzidine, × 400]

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  • What is the diagnosis or closest differential diagnosis?
  • What additional ancillary test(s) would be useful in this case?

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed

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Conflicts of interest

There are no conflicts of interest.

   Answer of Catechism (Quiz 3) Top

   Microscopic Findings Top

Biopsy showed a lesion composed of proliferating fibroblasts, randomly oriented and in short intersecting fascicles within a focally myxoid stroma. Towards the peripheral side of the lesion, as well as focally within the stroma, there were fragments of woven bone, lined by active osteoblasts and few multinucleate osteoclasts, imperceptibly lending with the fibroblasts [Figure 1]c and [Figure 1]d.


  1. What is the diagnosis? Answer: Myositis ossificans.
  2. Which category of tumors this entity comes under? Pseudosarcoma
  3. What is the recently described genetic event driving these group of tumors? USP6 rearrangement

   Discussion Top

According to the World Health Organization (WHO) classification of tumors of soft tissue and bone, myositis ossificans and fibro-osseous pseudotumor of digits (FP) and are self-limiting, localized lesions, essentially comprising two components, namely cellular fibrous tissue and reactive bone.[1] Invariably, these lesions are associated with a history of injury, which could not be procured in the present case. However, in view of involvement of the phalanx, which constitutes as one of the frequent location of this lesion; radiologic findings, combined with histopathologic features, diagnosis of MO was offered.

Various extraskeletal osseous lesions include myositis ossificans, fibro-osseous pseudotumor, fibrodysplasia ossificans progressiva, soft-tissue osteoma, and extraskeletal osteosarcoma.

Although myositis ossificans (MO) and FP are analogous lesions; it has been reported that unlike MO, FPs lack well-defined zoning pattern.[2] On radiologic imaging, while MO invariably appears as a well-defined, lytic lesion with a lucent centre and peripheral calcification, FP is characterized by an ill-defined soft tissue mass with focal calcification.[3] The present case, on radiologic imaging, was consistent with MO, while on microscopic examination had overlapping features between MO and FP. The other lesion in this spectrum is florid reactive periostitis, which additionally comprises chondroid elements. Lack of significant nuclear pleomorphism in the spindle cells and characteristic radiologic features, made diagnosis of an extraskeletal osteosarcoma, less likely. There have been earlier reports on FP and MO, involving the digits.[1],[4] Recently, USP6 rearrangement has been identified, as underlying genetic event, driving most MOs. Furthermore, this provides compelling evidence of a relationship of MO with nodular fasciitis and aneurysmal bone cyst.[5]

The presented case emphasizes upon combination of radiologic and histopathologic features, in formulating diagnosis of musculoskeletal tumors, especially the fibro osseous lesions.

   References Top

Rosenberg AE, Oliveira AM. Myositis ossificans and fibro-osseous pseudotumor of digits. In Fletcher CD, Bridge JA, Hogendoorn PC, Mertens F eds. World Health Organization Classification of Tumours of Soft Tissue and Bone. Lyon: IARC Press, 2013:p.50-1.  Back to cited text no. 1
Kransdorf MJ, Meis JM. From the archives of the AFIP. Extraskeletal osseous and cartilaginous tumors of the extremities. Radiographics 1993;13:853-84.  Back to cited text no. 2
De Smet AA, Norris MA, Fisher DR. Magnetic resonance imaging of myositis ossificans: analysis of seven cases. Skeletal Radiol 1992;21:503-7.  Back to cited text no. 3
Anand M, Deshmukh SD, Devasthali DA. Fibro-osseous pseudotumour of the metacarpal. J Hand Surg Eur 2011; 36: 701-2.  Back to cited text no. 4
Bekers EM, Eijkelenboom A, Grünberg K, Roverts RC, de Rooy JWJ, van der Geest ICM, et al. Myositis ossificans - Another condition with USP6 rearrangement, providing evidence of a relationship with nodular fasciitis and aneurysmal bone cyst. Ann Diagn Pathol 2018;34:56-59.  Back to cited text no. 5

Correspondence Address:
Bharat Rekhi
Room Number 818, Department of Surgical Pathology, Tata Memorial Hospital, 8th Floor, Annex Building, Dr. E.B. Road, Parel, Mumbai - 400 012, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/IJPM.IJPM_175_19

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