Giant plaque-type multinucleate cell angiohistiocytoma after total hip arthroplasty

Sir,

Multinucleate cell angiohistiocytoma is an entity comprising both mild vascular and fibrohistiocytic proliferation with scattered multinucleate cells.¹ It typically presents as papules arranged together in a single anatomic location, but less known clinical variations do exist.² Although considered a reactive process, its exact cause cannot be identified in many cases.^3,4

A 64-year-old male presented with a 13.5 × 9.5 cm ill-defined, violaceous indurated plaque on his left thigh [Figure 1]. The plaque had appeared two years back and was asymptomatic. There were no other notable skin findings. He was diagnosed with hypothyroidism and had undergone a total hip replacement surgery on the left side, nine years back, due to osteoarthritis.

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Figure 1:

Violaceous indurated plaque on a 64-year-old man’s left thigh.

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Histopathological examination revealed mild proliferation of small-sized vessels in the dermis, in conjunction with a perivascular inflammatory lymphohistiocytic infiltrate and abundant collagen bundles suggesting mild fibrosis [Figure 2a]. There were occasional cells which displayed multiple peripheral hyperchromatic nuclei [Figure 2b]. Both the histiocytic components of the infiltrate and multinucleated cells, stained with CD68. Signs of cellular atypia were not present and the epidermis was intact. These features were concordant with a diagnosis of multinucleate cell angiohistiocytoma.

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Figure 2a:

Mild vascular proliferation in the upper and mid dermis, mild fibrosis with abundant parallel collagen bundles and conspicuous perivascular infiltrate can be identified (Haematoxylin-eosin – 100x)

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Figure 2b:

Multinucleate cells of histiocytic appearance were identified between the abundant collagen bundles (Haematoxylin-eosin – ×400)

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As the lesion was benign and indolent, it was decided initially to follow an expectant line of management.

Eight months later, the patient showed a painful subcutaneous swelling within the plaque, without further changes. The tumefaction was tender, warm and fluctuant. Soft-tissue MRI showed a 4.3 × 2.2 × 4.5 cm space-occupying lesion in the subcutaneous plane of the proximal third of the left thigh, located at the same level as the femoral stem of the prosthesis, as well as signal alterations adjacent to its acetabular component. Our patient was diagnosed with prosthetic joint infection with extension to overlying soft tissue in the form of an abscess, which was successfully drained.

Multinucleate cell angiohistiocytoma is a type of benign fibrohistiocytic proliferation, reactive in nature.¹ It is believed to affect middle-aged females more frequently,² though some have not found any sex bias.¹ It typically presents as multiple erythematous, violaceous or brownish asymptomatic papules clustered in a given anatomical location, more commonly in the hands, face and lower limbs.² Multinucleate cell angiohistiocytoma in the form of small plaques, as well as generalised papules, has also been reported.²

In our case, however, this condition presented as a single, large-sized plaque. We have found only one additional case in the literature with such characteristics and we could not find any giant multinucleate cell angiohistiocytoma located over a joint prothesis.⁵ Clinical differential diagnoses include sarcoidosis, granuloma annulare and Kaposi sarcoma.² In fact, in this case, sarcoidosis and single plaque mycosis fungoides were initially considered.

Evidence has failed to show any association between multinucleate cell angiohistiocytoma and organic pathologies so far.¹ Although its pathogenesis remains unknown, factors such as local trauma, chronic inflammation and vascular injury have been put forward as inciting events.³ We found reports of only two other prosthesis-related cases along with this one, where the location of the abscess also hints at this hypothesis, suggesting that foreign material may play a role in eliciting this fibrohistiocytic reaction.³ The first one displayed lesions whose morphological features were not provided, over a knee prothesis.³ The second patient had lesions on his anterior thigh also next to a hip prosthesis, but multinucleate cell angiohistiocytoma presented as agminated papules.⁴

Classical pathological findings include mild vascular hyperplasia in the upper and mid dermis, fibrosis with parallel collagen bundles and an interstitial infiltrate with both mononucleate spindle-shaped histiocyte-like cells and scarce multinucleate cells.¹ Mononuclear histiocytes do usually stain for vimentin, CD68 and factor XIIIa, but are negative for S100.² This immunohistochemical profile confirms their fibrohistiocytic, possibly monocytic/macrophagic, lineage.¹ On the other hand, multinucleate cells feature angulated borders and peripherally arranged nuclei. They are vimentin-positive but demonstrate variable positivity with CD68 and fXIIIa.¹ Although a hallmark of this entity, they are not pathognomonic, as they can also appear with similar entities like fibrous papule and dermatofibroma.¹ Predominantly lymphocytic perivascular infiltrate is frequently noted which can include plasma cells, eosinophils and mast cells.²

Multinucleate cells have been thought to have fibroblastic nature due to their usual negativity for histiocytic markers.² Recent works have nevertheless proposed that they may represent degenerate histiocytes/macrophages which have lost their functions and IHQ markers.¹

Treatment is not necessary in the vast majority of cases as multinucleate cell angiohistiocytoma is a benign condition. Several therapeutic options such as surgical excision, CO2 and argon laser have been described.² These lesions tend to persist but there are some reports of spontaneous regression.³

We describe a case of giant multinucleate cell angiohistiocytoma likely to be precipitated by a total hip replacement surgery. Awareness regarding the triggers and varieties of this entity is important to avoid misdiagnosis.