|LETTER TO THE EDITOR
|Ahead of print publication
Plexiform schwannoma masquerading as an appendageal tumor
Swagata Tambe1, Priyanka Patil2, Hemangi Jerajani3
1 Innovation Skin Clinic and Laser Center, Mumbai, Maharashtra, India
2 Department of Dermatology, Suasth Hospital, Kalamboli, Navi Mumbai, Maharashtra, India
3 Department of Dermatology, MGM Medical College and Hospital, Navi Mumbai, Maharashtra, India
|Date of Submission||27-Apr-2020|
|Date of Decision||25-Jun-2020|
|Date of Acceptance||07-Aug-2020|
A-6/702, Saraf Chaudhary Nagar, Thakur Complex, Kandivali (E), Mumbai - 400 101, Maharashtra
Source of Support: None, Conflict of Interest: None
Schwannoma or neurilemmoma is true benign neoplasm of nerve sheath originating from Schwann cells. Schwannoma arises from nerve sheath of peripheral, cranial, or cutaneous nerves. Cutaneous schwannoma arise commonly from flexural aspect of extremities and head. Plexiform schwannoma is a rare subtype constituting 5% of all the types of schwannoma. Macroscopically, it grows in a plexiform or multinodular pattern, mimicking plexiform neurofibroma.
A 28-year-old male patient presented with an asymptomatic small skin-colored lesion of 7 months' duration gradually increasing in size over the occipital area of the scalp. On examination, the lesion was a solitary, soft, 0.5 cm in diameter skin-colored papule. On palpation, deeper nodular component was felt [Figure 1]. The nodular deeper part was freely mobile and minimally tender on palpation with the normal hair over the surface.
|Figure 1: Solitary, soft, 0.5 cm in diameter skin-colored papule on occipital area of scalp|
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Wide therapeutic wedge excision was done under local anesthesia [Figure 2]. The excised specimen showed a tumor mass in the dermis covered with thin fibrous capsule. Multi nodular well-defined encapsulated tumor masses of different sizes and shapes were seen in the dermal to subcutaneous tissue. The individual nodule composed of a hypercellular area (also called Antoni A type tissue) with proliferation of spindle cells, nuclei palisading around nodular to ribbon-like foci of fine fibrillary cell processes, Verocay bodies, and a hypocellular myxoid area (Antoni B type tissue) arranged in a nodular pattern confirming the diagnosis of plexiform schwannoma [Figure 3]a, [Figure 3]b, [Figure 3]c.
|Figure 3: (a) Multi nodular well-defined encapsuled tumor masses of different sizes and shapes in the dermal to subcutaneous tissue. (b) Multiple intradermal encapsulated nodules that vary in size and shape, and are separated from one another by loose or hyalinized fibrous stroma. (c) The individual nodule composed of a hypercellular area (also called Antoni A type tissue) with proliferation of spindle cells, nuclei palisading around nodular to ribbon-like foci of ?ne. A type t cell processes, Verocay bodies, and a hypocellular myxoid area (Antoni B type tissue) arranged in a nodular pattern|
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Diagnosis of the plexiform schwannoma was confirmed histologically, the patient was screened for acoustic schwannoma with magnetic resonance imaging (MRI) brain which did not reveal any abnormality. Final diagnosis of cutaneous plexiform schwannoma was considered.
Plexiform schwannomas (PS) are rare, benign, slowly growing, encapsulated tumors of Schwann cells arranged in plexiform pattern. Erlandson in 1985 classified Schwannomas into seven subtypes which is now widely used. It includes classical (Verocay), cranial nerve, cellular, plexiform (multinodular), ancient (degenerated), melanotic, and granular cell. Macroscopically, PS grows in a plexiform or multinodular or worm-like pattern. It affects predominantly young adults with either sex and occurs mostly as a slowly growing, rarely painful, solitary, or multiple nodular lesions on the trunk, head and neck, or upper extremities. Classic schwannomas exhibit a positive Tinel's sign (pain on percussion of the lesion) if originated from the major peripheral nerves.
Histopathologically, the PS is made up of multiple intradermal encapsulated nodules that vary in size and shape, and are separated from one another by loose or hyalinized fibrous stroma characterized by two types of patterns: central hypercellular Antoni type A and peripheral myxoid Antoni type B. This zonation corresponds to the target sign. Furthermore, palisades of nuclei and Verocay bodies characterized by acellular processes that separate adjacent rows of palisaded nuclei are often observed and most of the tumor consists of Antoni type A tissue. It displays diffuse and strong S-100 protein staining.
Immunohistochemical stains useful for the diagnosis of schwannoma are S100, epithelial membrane antigen, Leu-7, myelin basic protein, CD 34, CD 68, collagen types 1, 3, and 4, and vimentin.
PS shows a specific multinodular pattern and hypointense capsule that separated the tumor from surrounding soft tissue on T2-weighted MRI.
Plexiform schwannoma can be associated with neurofibromatosis type 2 but it is not associated with von Recklinghausen disease or a higher risk for malignant transformation.
The differential diagnosis of PS includes plexiform neurofibroma, plexiform fibrohistiocytic tumor, malignant peripheral nerve sheath tumors, palisaded encapsulated neuroma, and neurotropic melanoma. In general, surgical excision is the treatment of choice.
In conclusion, PS is rare and often misdiagnosed. It should be considered in the differentials of asymptomatic, round cystic swelling over scalp. Unique feature of our case is different clinical presentation of the tumor with papular superficial component mimicking an appendageal tumor and hidden deep nodular component.
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.
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[Figure 1], [Figure 2], [Figure 3]