Fibrosseous pseudotumor of the digit: a clinicopathologic study of 43 new cases

[Fibro-osseous pseudotumor of the digits: An exemple of USP6-related fibroblastic/myofibroblastic tumor]

Fibro-osseous pseudotumor of the digits is a benign tumour closely related to myositis ossificans. It is a rare lesion seldom reported in the literature. We report the case of a 33-year-old woman with lancinating pain in the first phalanx of the second finger of the right hand, associated with inflammation. The histopathological examination of the surgical excision biopsy of the lesion revealed a spindle-shaped proliferation within a sclerosing, hyaline, and osteoid stroma. In our observation, immunohistochemistry and molecular biology are the main elements that helped to establish the diagnosis and eliminate the various differential diagnoses, despite a non-specific histopathological aspect.

Fibro-Osseus Pseudotumor of the Digit: A Case Report and Review of Literature

Introduction

Bony subungual growths arising on the digital tip are uncommon. Among these, subungual exostosis is a common cause.

Case Presentation

We describe a 35-year-old-male patient with a rare occurrence of a fibro-osseus pseudotumor of the digit. It presents with reactive intramembranous ossification, with no continuity with the distal phalanx, helping differentiate it from a subungual exostosis. The patient presented with an asymptomatic subungual growth, lifting up the nail plate distally causing onycholysis. The characteristic clinical, radiological, and histopathological features of the case are described, which helped confirm the diagnosis.

Conclusion

Cases with fibro-osseus pseudotumor of the digit reported in literature are reviewed comprehensively. The factors helping differentiate this from the other bony tumors affecting the distal phalanx, including subungual exostosis, myositis ossificans, and osteosarcoma are also highlighted.

Primary cutaneous extraskeletal osteosarcoma: a series of 16 cases

Extraskeletal osteosarcoma (EOS) is a high grade soft tissue tumour characterised by the production of malignant osteoid, without attachment/involvement of underlying bone/periosteum. Rarely, EOS presents as a cutaneous tumour. The clinical behaviour of primary cutaneous EOS (PC-EOS) remains incompletely characterised. Herein we present the largest case series of PC-EOS reported to date. Sixteen PC-EOS cases from the archives/consultation files were retrieved (male:female 1:1; age 31-96 years, mean age 66 years). The tumours measured 1-10 cm (mean 3.2 cm) and were located on the lower extremity (7), head (6), upper extremity (2), and trunk (1). They consisted of pleomorphic, spindled-to-epithelioid cells, with fascicular, nodular, or sheet-like growth patterns and foci of malignant osteoid. Immunohistochemistry did not reveal specific lines of differentiation, and there was no evidence of other tumour types. A literature review was conducted to identify all well characterised cases of PC-EOS. A combined analysis of present and past cases was performed to determine overall trends in clinical characteristics and outcomes. The mean follow-up period was 23.9 months, during which 67.5% of patients experienced progression-free survival and 18% of patients died of disease. Rates of local recurrence and metastasis were 10% and 25%, respectively, approximately double past estimates. These data suggest that the prognosis of PC-EOS is less favourable than previously thought. The differential diagnosis includes benign entities (e.g., ossifying pyogenic granuloma) and malignant neoplasms with heterologous osteosarcomatous differentiation (e.g., carcinosarcoma, transdifferentiated melanoma). Wide excision remains the standard of care, and the role of chemotherapy and radiation remains inconclusive. Recognition of this rare entity can facilitate prompt diagnosis and appropriate treatment.

Multimodality imaging features of USP6-associated neoplasms

Since the discovery of USP6 gene rearrangements in aneurysmal bone cysts nearly 20 years ago, we have come to recognize that there is a family of USP6-driven mesenchymal neoplasms with overlapping clinical, morphologic, and imaging features. This family of neoplasms now includes myositis ossificans, aneurysmal bone cyst, nodular fasciitis, fibroma of tendon sheath, fibro-osseous pseudotumor of digits, and their associated variants. While generally benign and in many cases self-limiting, these lesions may undergo rapid growth, and be confused with malignant bone and soft tissue lesions, both clinically and on imaging. The purpose of this article is to review the imaging characteristics of the spectrum of USP6-driven neoplasms, highlight key features that allow distinction from malignant bone or soft tissue lesions, and discuss the role of imaging and molecular analysis in diagnosis.

[Fibro-osseous Pseudotumor of the first Web Space - an interesting Case]

Ein 52-jähriger Patient stellte sich nach Zuweisung durch seinen Hausarzt aufgrund einer schmerzhaften, größenprogredienten Schwellung in der ersten Kommissur seiner linken adominanten Hand in der handchirurgischen Sprechstunde vor. Er gab an, die Schwellung vor fünf Wochen erstmals bemerkt zu haben und dass sie zunehmend schmerzhaft und funktionell einschränkend sei. Ein aktuell auslösendes Trauma wurde verneint; allerdings habe er sich vor drei Jahren bei einem Fahrradsturz im Bereich der betroffenen 1. Kommissur verletzt. Die Familienanamnese war bzgl. maligner Erkrankungen blande.

Fibro-osseous pseudotumor of the digit: a case report

Fibro-osseous pseudotumor is a poorly reported benign ossifying tumor. Due to its aggressiveness and lack of specificity, the lesion has previously been mistaken for a malignant lesion, leading to unnecessary radical treatment. Our case warns our readers of the aggressiveness of the tumor and rational surgical planning. In our case, a 25-year-old male patient presented with a painless, enlarging mass in the left index finger that had developed over the course of 5 months. The lesion was first partially surgically removed for biopsy, which confirmed the lesion to be fibro-osseous pseudotumor. Considering the possibility of skin necrosis from complete excision, complete removal was postponed until the second surgery. However, the residual lesion rapidly progressed, reaching its original size within 4 months. Another lesionectomy was performed to thoroughly remove the recurrent lesion surrounding the joint capsules. The intraoperative frozen section again supported the initial diagnosis and recurrence. During the 2-year follow-up, there were no signs of recurrence, and the function of the finger was fully recovered. Fibro-osseous pseudotumor should be considered in the differential diagnosis of rapidly progressive lesions affecting the digits. Complete surgical excision is the treatment of choice. However, the surgical strategy should be cautiously planned because of the aggressiveness of fibro-osseous pseudotumor and the possibility of saving the involved digit.

Fibro-Osseous Pseudotumor Arising From Nail Bed of the Great Toe: A Rare Case of Recurrence

A fibro-osseous pseudotumor (FOPT) is a rare, rapidly enlarging, benign soft-tissue neoplasm that presents with localized pain, swelling, and redness. It typically presents in the hands and much less frequently in the feet. FOPT is characterized histologically by foci of osseous differentiation within the proliferated fibroblasts. This must be differentiated from other benign and malignant lesions. FOPT of the toes has been described in a few reports, but recurrence, following surgical excision, is extremely rare. Here we report a young, healthy female patient who presented with a rapidly growing FOPT of the left great toe. This unusual case had recurred twice following surgical excision, all within a 2-month period of time. The lesion was again completely excised, with no recurrences at follow-ups of 18 and 36 months. In conclusion, FOPT is a rare soft tissue lesion of the toes. It features fibroblastic proliferation and osseous differentiation, which needs to be differentiated from other benign and malignant tumors. The standard treatment is complete surgical excision with an excellent prognosis.

Fibro-Osseous Pseudotumor

Fibro-osseous pseudotumor is an extremely rare subcutaneous benign ossifying lesion associated with bone formation that is most commonly seen in the hands, followed by the toes. Because the tumor has a certain degree of invasiveness, it is often mistaken for malignancy, which leads to radical, excessive treatment. Our case involved a 32-year-old man with lesions on the left index finger. We documented the detailed data of diagnosis, treatment, and follow-up. We also conducted a review and summarized the published cases to advance our understanding of the disease, provide more accurate diagnostic criteria, and avoid inappropriate surgical procedures. [Orthopedics. 2021;44(6):e713-e718.].

Fibro-osseous Pseudotumor of the Distal Phalanx

Fibro-osseous pseudotumor of the digit is an unusual benign tumor that appears on the extremities. A 45-year-old, human immunodeficiency virus-positive man presented with a painful lesion on the tip of the fourth toe of his right foot. The tumor was completely excised without any connection to the underlying bone being observed, although the phalanx had to be extirpated. Histopathology confirmed the diagnosis of fibro-osseous pseudotumor. At the follow-up visit, 12 months later, no abnormalities were found.

Benign growing mass of the digit presenting as an ulcerated mass - case report and review of the literature

A 68 year-old female presents with an ulcerated mass of the 5th digit, with rapid growth during the previous month to surgery. The mass was excised and covered with a 4th dorsal metacarpal artery perforator flap. The histologic analysis was compatible with the diagnosis of fibro-osseous pseudotumor of the digit.

Ossifying pyogenic granuloma: A rare variant usually not recognized

Pyogenic granuloma (PG) represents a polypoid and lobular, capillary lesion, resembling granulation tissue, usually occurring on skin or mucosal surfaces. The occurrence of metaplastic ossification is extremely rare in PG. We present three cases of PG with metaplastic ossification. All three patients were men, aged 18-66 years. In all cases, the lesions occurred on the digits, particularly in or around the nail bed. Histopathologically, these superficial dermal-based tumors were characterized by classic features of PG, namely circumscribed, exophytic to polypoid proliferations of capillary-sized blood vessels in a lobular arrangement. The characteristic vascular component also was intimately associated with spicules and trabeculae of metaplastic bone formation rimmed by osteoblasts and osteoclasts. This osseous component was diffusely distributed in two cases and more localized in another. We speculate that ossification in PGs possibly represents a reactive process in response to chronic injury. We believe that ossifying PG is likely under-recognized and often mistaken for other entities also arising in the extremities and characterized by osseous metaplasia.

Ubiquitin-specific Peptidase 6 (USP6)-associated Fibroblastic/Myofibroblastic Tumors: Evolving Concepts

Ubiquitin-specific peptidase 6 (USP6) is a hominoid-specific gene residing on chromosome 17p13 and serves as a deubiquitinating enzyme with a diverse set of functions including intracellular trafficking, inflammatory signaling, cell transformation and protein turnover. USP6 rearrangements were first identified in aneurysmal bone cysts, resulting in promoter swapping and over-expression of wild type USP6. Several morphologically overlapping fibroblastic/myofibroblastic tumors are known to harbor USP6 rearrangements, including nodular fasciitis, cellular fibroma of tendon sheath, myositis ossificans and fibro-osseous pseudotumor of digits. Over the past few years, fusions involving the USP6 gene and various partner genes have been described in these neoplasms. The current World Health Organization Classification of Tumors of Soft Tissue suggests that USP6-rearranged lesions are typically benign and usually self-limited in their growth. This review provides an updated overview of the clinical, histological and molecular genetic features of USP6-associated fibroblastic/myofibroblastic tumors and discusses how these lesions should be best classified.

Acute calcific periarthritis of the proximal phalangeal joint on the fifth finger: A case report and literature review

RATIONALE

Acute calcium deposits, including acute calcific periarthritis or acute calcific peritendinitis, are benign calcifying soft tissue lesions that have a self-resolving course. These calcifying lesions usually develop in the shoulder, while acute calcific periarthritis in the digits is uncommon. When acute calcific periarthritis involves the digits, the lesion occasionally mimics other benign calcifying or ossifying lesions and can easily be misdiagnosed, resulting in unnecessary diagnostic studies and treatment. We present a rare case of acute calcific periarthritis around the proximal phalangeal joint of the left fifth finger that took a long time to spontaneously resolve, and review previous reports of similar cases.

PATIENT CONCERNS

A 69-year-old woman complained of longstanding pain and swelling of the fifth finger of the left hand. She had visited several clinics and hospitals and had been treated with analgesics and splinting for more than 2 months, but the pain in the finger had gradually worsened.

DIAGNOSES

Blood chemistry analysis showed no signs of inflammation or other abnormalities. Radiographs revealed a well-defined subcutaneous calcifying lesion without bony destruction, suggesting a benign calcification process. Computed tomography and magnetic resonance imaging led to a diagnosis of acute calcific periarthritis of the proximal interphalangeal joint of the fifth finger.

INTERVENTIONS

An excisional biopsy was recommended to achieve a definitive diagnosis, but this was declined by the patient. Thus, no invasive treatments were administered, and she was treated with analgesics and encouraged to massage the affected finger.

OUTCOMES

The pain gradually improved, and follow-up radiographs showed complete disappearance of the calcifying mass 6 months after the initial visit to our hospital, without recurrence during a follow-up period of more than 2 years.

LESSONS

Acute calcific periarthritis is diagnosed based on history, clinical examination, and imaging findings, which provide evidence for the diagnosis of calcium deposition in the digits even if the lesions have been present for a long time. Watchful observation is an appropriate treatment strategy for acute calcific periarthritis of the digits.

Rapidly growing Fibro-osseous pseudotumor of the digit: A case report

INTRODUCTION

Fibro-osseous pseudotumor of the digit is a rare benign lesion of subcutaneous tissue that typically arises in the parabone site of the proximal phalanx in young adult females. The lesion is histopathologically characterized by fibroblastic proliferation and osteoid formation. Good prognosis following complete surgical excision of the tumor has been reported, with a very low recurrence rate and no reports of malignant transformation. Despite its benign clinical behavior, the lesion can be mistaken for a malignant neoplasm, such as an extraskeletal or parosteal osteosarcoma, in case of rapid growth, thereby rendering the diagnosis challenging.

PATIENT CONCERNS

We report the case of a 30-year-old right-handed male who presented to our hospital with a rapidly growing mass on the dorsal aspect of the right little finger.

DIAGNOSIS

The patient was suspected to have soft tissue tumor of the little finger. The lesion could be considered a malignant tumor on the basis of clinical findings.

INTERVENTIONS

The patient underwent surgery for exploration and excision of the mass.

OUTCOMES

The excised mass was diagnosed to be fibro-osseous pseudotumor of the digit upon histological assessment. Postoperatively, the wound healed without complications. At postoperative 6 months, there were no signs or symptoms of recurrence, and the patient returned to his premorbid functional status.

CONCLUSION

Following the detection of a soft tissue mass with clinicopathological features of pseudomalignancy in the digit, clinicians should consider fibro-osseous pseudotumor of the digit as a possible diagnosis, thereby avoiding unnecessary aggressive surgery.

USP6-Associated Neoplasms: A Rapidly Expanding Family of Lesions

Nearly 20 years ago, the first description of a translocation involving chromosome 17 on which USP6 resides was described. Since then, not only the culprit gene but also many fusion partners, leading to transcriptional activation of USP6, have been detected. The first neoplasm known to harbor USP6 rearrangements was aneurysmal bone cyst. Since then, other entities like nodular fasciitis, myositis ossificans, fibro-osseous pseudotumor of digits, and a subgroup of fibromas of tendon sheath, probably representing tenosynovial nodular fasciitis, have been added to the list of USP6-rearranged lesions. Remarkably, all of them share clinical as well as morphological characteristics, and authors have suggested that these entities actually belong to the same spectrum. This review summarizes the current knowledge regarding USP6-rearranged lesions and further elaborates on how these neoplasms relate to one another. We propose to call these lesions UAN (Usp6-associated neoplasm).

Fibro-osseous pseudotumour of the digit-a diagnostic challenge

A 60-year-old right-hand dominant woman presented to the emergency department with a 3-week history of pain and swelling in her right thumb. The X-ray showed evidence of erosion at the tip of the distal phalanx. Her initial management included surgical debridement with bone biopsies and intravenous antibiotics. The initial working diagnosis was a soft tissue infection of the thumb tip, causing osteomyelitis of the distal phalanx. The X-ray findings also raised the suspicion of a possible bone tumour. She was treated as having osteomyelitis and attended ambulatory care for daily intravenous antibiotics for 2 weeks. Initial histology was reported as a spindle cell tumour; however, following discussion at the sarcoma MDT, a diagnosis of a fibro-osseous pseudotumour of the digit was made. This is a benign lesion that was managed non-operatively in this patient. This case emphasises the importance of considering all differential diagnoses, even in a common presentation.

Idiopathic aggressive myositis ossificans of the hand infiltrating the flexor sheath/checkrein ligament, obliterating the common digital artery, and attenuating the digital nerve: A case report

•

Myositis ossificans of the hand is extremely rare.

•

These tumors do not usually infiltrate adjacent structures.

•

We present a case with infiltration of adjacent structures.

•

Complete excision was curative.

Introduction

Myositis ossificans of the hand is extremely rare and tumors do not usually infiltrate adjacent structures. We present a very unusual case with a tumor infiltrating adjacent structures.

Report of a case

A 30-year-old female presented with a 5-week history of a painful rapidly-growing mass over the proximal phalanx of the right ring finger. The mass infiltrated the entire flexor sheath over the proximal phalanx as well as the checkrein ligament of the proximal interphalangeal joint. The common digital artery of the 3rd web space was obliterated by the tumor. The radial digital nerve of the ring finger was stretched and attenuated. Total excision was done and histology confirmed the diagnosis of myositis ossificans. No recurrence was seen at the one-year follow-up.

Discussion

Myositis ossificans of the hand is extremely rare. We report our case to document the unique feature of tumor infiltration of adjacent structures. We also document that excision is curative despite the infiltrative nature of the tumor.

Conclusion

Our case is unique because of the infiltrative nature of tumor. There is no indication for amputation even for infiltrative tumors. We demonstrate that complete excision is curative with good regain of function even in infiltrative lesions.

Fibro-Osseous Pseudotumor of the Hand

Fibro-osseous pseudotumor of digits (FOPD) is an uncommon histological diagnosis. Clinical and imaging findings may resemble high-grade sarcoma or infection. We describe a patient with progressive pain and swelling at the dorsal surface of the first web space. MRI and CT imaging revealed an intramuscular heterogenous soft tissue mass defined by a mineralized peripheral ring. Core needle biopsy diagnosed FOPD. Eight months later a matured ossified nodule that was quite smaller than the initial soft tissue mass was excised. The patient is symptom free without local recurrence at 1 year follow up. Soft tissue masses of the hand pose a challenging diagnostic and therapeutic issue. An in depth interpretation of clinical, imaging and histology findings is important to avoid erroneous diagnosis and treatment.

Fibro-osseous pseudotumor of the digit: Case report and surgical experience with extensive digital lesion abutting on neurovascular bundles

Background

Fibro-osseous pseudotumor (FOPD) of the digit is a rare benign lesion of subcutaneous tissue characterized by fibroblastic proliferation and osteoid formation. Herein, we present a case of massive FOPD lesion in the base of ring finger with extensive involvement of the neurovascular bundles with challenging surgical approach.

Case description

A 27-year old female patient, presented with 7-months history of a progressively enlarging mass on her left hand. Upon assessment, the mass was located over the proximal phalanx of the left ring finger with extensive involvement of the 4th web space. Her neurovascular examination was normal. Radiological investigations showed partial involvement of the radial sided bundle together with complete involvement of the ulnar sided neurovascular bundle. The patient was bothered by the mass being painful with overlying skin ulceration. She was taken afterwards to the operating room where the mass was dissected freely from those bundles while preserving the radial and ulnar structures. The resected margins were however, positive for residual lesions due to the extensive nature of the mass. The patient was informed about the need for close follow-ups for both clinical and radiological signs of lesion recurrence pending early surgical intervention.

Conclusion

FOPD although benign, a soft tissue osteosarcoma is one of the differential diagnosis. Meticulous attention to the clinical, pathological and histological features of FOPD is required. Early diagnosis and treatment of FOPD is very crucial in optimizing the overall outcome. Pre-operative planning with various radiological modalities was of great help anticipating the surgical course.

•

Fibro-osseous pseudotumor (FOPD) of the digit is a rare benign lesion of subcutaneous tissue.

•

The differential diagnosis includes: myositis ossificans, extraskeletal osteosarcoma, parosteal osteosarcoma.

•

Meticulous pre-operative planning is of great importance to optimize patient outcome.

•

Fibro-osseous pseudotumor (FOPD) although benign, complete excision assure lack of recurrence.

•

Meticulous histological assessment for any features of malignancy assure proper patient outcome.

Management of Myositis Ossificans of the Hand: A Case Report and a Review of the Literature

Myositis ossificans is a rare form of self-limiting heterotopic ossification of muscles. Most cases are seen in the thigh; the standard approach to these cases has been nonsurgical management awaiting spontaneous resolution. We report on a rare case of myositis ossificans of the hand with severe symptoms treated with early marginal excision without a trial of nonsurgical management.

Fibro-Osseous Pseudotumor of the Digits Mimicking Pyogenic Granuloma

Fibro-osseous pseudotumor of the digits is a benign neoplasm that originates in the soft tissue adjacent to the short bones of the hands and feet. We present a case in a 13-year-old girl that was initially misdiagnosed as pyogenic granuloma. Familiarity with this entity and imaging and histologic studies are necessary to avoid incorrect diagnoses and aggressive surgical interventions.

Acral manifestations of soft tissue tumors

This group of biologically diverse entities is united by topographic localization to the hands and feet. Categorizing tumors by body site narrows the differential into a short list of possibilities that can facilitate accurate and rapid diagnosis. The goal of this review is to provide a practical approach to soft tissue tumors of acral locations for clinicians, pathologists, and researchers alike. What ensues in the following text is that tight coupling of the clinical picture and histopathologic findings should produce the correct diagnosis, or at least an abbreviated differential. The salient clinicopathologic, immunohistochemical, and molecular features are presented alongside current treatment recommendations for each entity.

Fibro-Osseous Pseudotumour of the Digit: An Illustrative Case and Review of the Literature

Fibro-osseous pseudotumour is a rare, benign ossifying tumour of soft tissue that should be considered in the differential diagnosis of any tumour affecting the digits. Clinical diagnosis is difficult and fibro-osseous pseudotumour is often mistaken for malignancy, leading to inappropriate treatment. Knowledge of its clinical and histopathological features thus allows for appropriate primary treatment, sparing the patient from unnecessary radical surgery associated with presumed malignancy. We present the case of a 48-year-old male with fibro-osseous pseudotumour affecting the right ring finger, successfully treated with local excision. This is the second reported Australian case of fibro-osseous pseudotumour, and we present an extensive review of the literature relating to the diagnosis and management of this rare tumour.

Subungual fibro-osseous pseudotumour of the toe

Subungual fibro-osseous pseudotumour of the toe is a rare osseous soft tissue tumour of which only six cases have been described in the literature. We present a case in a teenage boy that posed an instructive diagnostic challenge and discuss the distinguishing features of the various differential diagnoses. The subungual location is very rare. For such tumours, radiology is as vital as histopathology in making a diagnosis and excluding neoplasia. Accurate diagnosis requires careful clinico-pathological and radiological correlation. These sorts of lesions may present to the dermatologist, not always the foot surgeon.

Fibro-osseous pseudotumor of the digit presenting as an ulcerated lesion: a case report

Fibro-osseous pseudotumor of the digit is rare benign lesion of subcutaneous tissue which is thought to be reactive process as a result of repeated trauma. We report a case of an ulcerated lesion of skin of middle finger, clinically thought to be leishmaniasis which after punch biopsy followed by excision turned out to be fibrosseous pseudotumor. Diagnosis of fibro-osseous pseudotumor requires immense precision as it can clinically mimic unungal exostosis and can sometimes be misinterpreted clinically and radiologically as myositis ossificans. We suggested an algorithimic approach for histopathologic assessment of fibro-osseous soft tissue lesions with evaluation of both stromal and osseous components. Bland fibroblastic stroma, mature osseous component with prominent osteoblastic rimming and absence of zonation pattern will support the diagnosis of fibro-osseous pseudotumor especially if located at a superficial and distal location.

Florid reactive periostitis of the metacarpal and phalanx: 2 case reports

Florid reactive periostitis is a rare benign fibro-osseous proliferative lesion of soft tissue and is mainly composed of fibrous connective tissue and mature bone. The lesion usually occurs in the finger and seldom in the metacarpal. The lesion mimics malignant and infectious disorders, thus often leading to inappropriate treatment. Radiography usually shows an ossified mass attached to the underlying hand bones without interruption of the cortex. We report 1 case of florid reactive periostitis with unossified mass and underlying bone marrow edema in the metacarpal of hand and 1 case with adjacent cortical destruction in the phalanx. In addition, we describe the imaging findings of computed tomography CT and magnetic resonance imaging MRI and discuss their diagnostic values compared with routine radiographic examination.

Fibro-osseous pseudotumor of the digit

Fibro-osseous pseudotumor of the digit is an unusual ossifying soft tissue lesion, which is usually an ill-defined soft tissue mass in radiography, with focal calcification, especially in the proximal phalanx. It predominantly affects young adults and, unlike myositis ossificans, is more common in women. The current case is a 30-year-old man who presented with pain and swelling on the dorsum of middle phalanx of the left index finger without history of trauma. Diagnosis of this lesion requires a high index of suspicion and should be differentiated from myositis ossificans, turret exostosis, and extra-skeletal osteosarcoma, which are discussed. This lesion is considered benign and has an excellent prognosis following complete removal and local recurrence is unusual. No cases of malignant change are on record.

An unusual case of subungal ossification in the finger

We report the case of a painless deforming subungual mass at the nail tip, progressively enlarging over three months. Radiographs showed an extra-osseous ossification. Intraoperatively this was found to be a bony mass arising from the sterile matrix. Unusual extra-osseous ossification in the finger is rare and this case highlights the need of this benign lesion to be considered when a patient presents with finger swellings.

Calcifying pseudoneoplasm of the cerebellopontine angle: case report

BACKGROUND AND IMPORTANCE

Calcifying pseudoneoplasms are rare tumors of the neuraxis. To our knowledge, this is only the second reported case in the literature of calcifying pseudoneoplasm of the cerebellopontine angle. The etiology and natural history of these neoplasms are not well understood. This case report provides a thorough review of the histology and potential origins of calcifying pseudoneoplasm.

CLINICAL PRESENTATION

A 34-year-old previously healthy man presented with a 6-month history of progressive worsening headaches, fatigue, tinnitus, dizziness, and blurry vision. Neurological examination was notable for tongue deviation, tongue atrophy, and left uvula deviation. Computed tomography (CT) scanning showed a 3.3 × 3.5 cm densely calcified posterior fossa mass appearing to arise from the occipital bone. Magnetic resonance imaging (MRI) revealed a 4.3 × 2.9 × 2.9 cm left posterior fossa enhancing mass with the margin tip from the left occipital condyle. A transcondylar approach was used to resect the lesion. The mass was found to have eroded through the bone into the foramen magnum. Histopathological examination confirmed the diagnosis of calcifying pseudoneoplasm of the cerebellopontine angle.

CONCLUSION

Calcifying pseudoneoplasms should be considered in the differential diagnosis of calcified cerebellopontine angle tumors. Histopathologic diagnosis is extremely important in the characterization of these lesions in order to direct the course of appropriate management. An inaccurate diagnosis of a malignant tumor can result in potentially harmful and unnecessary therapies, as prognosis for these lesions is generally favorable.

Fibro-osseous pseudotumor of the digit: a clinicopathological study of 17 cases

Fibro-osseous pseudotumor (FP) of the digit is a rare, non-neoplastic heterotopic ossifying lesion involving the subcutaneous tissues of the digits. To date, there are only a few published series in the literature. Our study of 17 cases, retrieved from the authors' referral archives, shows that the condition chiefly affects young to middle-aged adults (median = 34 years), with a slight female predominance and involves the fingers (n = 8) and toes (n = 8). One identical lesion was identified on the forehead (n = 1). Lesional size ranges from 0.8 to 5.6 cm. Treatment was by surgical excision. Histologically, 14 cases show a fairly well-circumscribed dermal (n = 10) or dermal and subcutaneous (n = 7) lesion with surface ulceration (n = 7). The lesion is composed of fascicles of variably cellular, spindle-shaped cells [calponin (n = 14) and smooth muscle actin (SMA) (n = 11) positivity], with minimal to mild atypia (n = 5), dispersed in a myxoid stroma, focally reminiscent of nodular fasciitis. At least focal irregular trabeculae with osteoid formation and osteoblastic rimming are seen in all cases. The main differential diagnosis is an extraskeletal osteosarcoma; however, this afflicts an older age group, with prominent cytological atypia and atypical mitoses. Clinical follow-up (range: 18 months - 14 years, n = 12) reveals evidence of local recurrence in some cases (n = 2), but no evidence of metastases. In conclusion, we report an additional 17 cases of this rare lesion to increase awareness amongst dermatopathologists.

[Fibro-osseous pseudotumor of the thumb. Report of a case]

Fibro-osseous tumor of the digits is an uncommon, benign condition with an excellent prognosis after local excision. Like myositis ossificans, clinical and histological features may mimic a malignant tumour, especially an extraskeletal osteosarcoma. A correct interpretation of clinical, radiological and histological data is a prerequisite to avoid misdiagnosis and unnecessary radical surgery (for example, amputation). We report the case of a 15-year-old boy who presented with a slow-growing mass of the left thumb, which turned out to be a fibro-osseous tumor on microscopic examination. A complete excision was performed without loss of function. Fifteen months postoperatively, there was no local recurrence.

Cutaneous myositis ossificans: an appropriate descriptor for fibro-osseous lesion of the external auditory canal

Myositis ossificans is a benign pseudosarcomatous bone-forming lesion, histologically characterized by 2 components: a spindle (myo)fibroblastic cell population and a bony component that is arranged in a "zonal" pattern. It mainly affects the deep soft tissues of limbs, but its occurrence in other unusual locations, such as abdomen, inside nerves, and the subcutaneous fat, has been reported. The existence of myositis ossificans restricted to the skin has rarely been published under the term "fibro-osseous lesion of the external auditory canal." Here, we describe an additional case in the external auditory canal, emphasizing its differential diagnosis and alerting dermatopathologists and pathologists to the possibility of encountering such lesion in this anatomic location. For purposes of unifying terms, we propose that cases similar to ours be called "cutaneous myositis ossificans" instead of fibro-osseous lesion of the external auditory canal.