Open AcceCase ReportPilomatrix carcinoma presenting as an extra axial mass: clinicopathological featuresNoel J Aherne*1, David A Fitzpatrick1, David Gibbons2 and John G Armstrong1
Address: 1Department of Radiation Oncology, St. Luke's Hospital, Dublin, Ireland and 2Department of Pathology, St. Luke's Hospital, Dublin, Ireland
AbstractPilomatrix carcinoma is the rare malignant counterpart of pilomatrixoma, a skin adnexal tumouroriginating from hair matrix cells. Pilomatrix carcinoma can arise as a solitary lesion de novo, orthrough transformation of a pilomatrixoma. Pilomatrixoma was first described erroneously asbeing of sebaceous gland origin but was later discovered to be derived from hair matrix cells. Theyare rare, slow growing tumours of the skin found in the lower dermis and subcutaneous fat and arepredominantly found in the neck and the scalp. While known to be locally aggressive, no malignantform was thought to exist until it was described relatively recently. Since then, approximatelyninety cases of pilomatrix carcinoma have been reported.
We report the case of a 41 year old mentally retarded male who had a longstanding lesion in theleft neck for approximately fifteen years previously diagnosed as a pilomatrixoma. He presentedwith severe headache, falls and visual disturbance and a biopsy showed pilomatrix carcinoma of theoccipital region which, on computed tomography ( CT ) invaded the occipital bone, the cerebellumand the left temporal lobe. At his initial presentation he had a craniotomy and subtotal excision ofthe lesion but received no adjuvant therapy. After an early intracranial recurrence he had furtherdebulking and adjuvant external beam radiotherapy. He has had no further intracranial recurrenceafter three and a half years of follow-up. Here we present the pathological features of thisuncommon tumour.
BackgroundPilomatrix carcinomas are the aggressive variant of pilo-matrixomas, a type of hair matrix tumour. Although ini-tially thought to be benign when first described byMalherbe and Chenantais [1], as early as 1927 Gromiko[2] noted that some tumours had biologically aggressivebehaviour. In 1980, Lopansri and Mihm [3] reviewed sixcases of biologically aggressive pilomatrixoma. They
found that the major discriminators of malignancy whencompared to pilomatrixomas were the presence of hyper-chromatic, vesicular basaloid cells with numerous mitosesand infiltration into adjacent tissue or blood vessels. Theyare characterised by sheets and islands of proliferatingatypical basaloid cells with an infiltrating border. Thiscase demonstrates an unusual pattern of local spread intothe cranial cavity.
Case presentationA 41 year old male presented with a cutaneous tumour inthe left posterior triangle of the neck which had beenpresent for at least fifteen years. He had a history of mildmental retardation, bilateral undescended testes and hadundergone appendicectomy as a child. He was otherwisewell and in fulltime employment. He had multiple priorresections of the neck lesion which revealed benign pilo-matrixoma. The recurrent mass measured 4.5 centimetresand was resected with clear margins. Pathologic analysisrevealed a pilomatrix carcinoma. The patient had no fur-ther treatment at that time.
He represented 7 months later with a two week history offalls associated with severe occipital headache, visual dis-turbance and a left sided neck mass. Prior to neurosurgicalevaluation a Magnetic Resonance (MR) scan was per-formed (Figure 1). This showed a 5.5 × 4 × 5 centimetremass arising from the extra-axial tissues. This mass had alarge intra-cranial component causing significant com-pression of the left side of the cerebellum with some masseffect. There was associated midline shift and thrombosisof the right transverse sinus. The patient proceeded to pos-terior fossa exploration and subtotal resection.
On postoperative MR imaging of the area an early recur-rence was identified at three months, necessitating furthersubtotal debulking. He was then referred for adjuvantradiation therapy. The patient received fractionated threedimensional external beam radiation therapy to theocciput and left neck to a total dose of 50 Gy in 25 frac-tions. Serial follow-up MR scans have shown no progres-sion in size of the intracranial component and the patientremains asymptomatic after 42 months follow-up.
In our case, haematoxylin and eosin stained sections (Fig-ure 2a) of the recurrent tumour mass show characteristicfeatures of pilomatrixoma. These include both basaloidand squamous epithelium with abrupt keratinization giv-ing the characteristic 'ghost' cells. A loose fibrovascularstroma is seen and dystrophic calcification and ossifica-tion are also present. The basaloid element is hyperchro-matic and in areas shows a brisk mitotic rate, includingabnormal forms. An immunohistochemical stain for theproliferation marker Ki-67 (MIB1) (Figure 2b) shows thebasaloid cells to be actively proliferating with more than50% of nuclei positive in areas. No vascular space inva-sion is seen. These histologic features, supported by theimmunohistochemistry and the clinical course allow adiagnosis of pilomatrix carcinoma to be made. In pub-lished series, the most reliable indicators of malignancy inpilomatrixomas are atypical and frequent mitoses, nuclearpleomorphism, central necrosis, ulceration and infiltra-tion of skin, soft tissue, blood vessels or lymphatics [4].
DiscussionSince Lopansri and Mihm first noted the existence of pilo-matrix carcinomas in 1980 there have been fewer thanninety cases descibed and there has been only one previ-ously reported case of invasion of the cranial vault [5]. Inthe decades since Gromiko [2] noted the aggressive behav-iour of some pilomatrixomas they had been thought tofollow an indolent course with little or no potential formetastasis. The morphological features of pilomatrix car-cinomas appear to be nuclear pleomorphism, frequentand atypical mitoses, central necrosis, infiltration of skinand soft tissues, blood and lymphatic vessel infiltration,and ulceration [4,6,7]. The major diagnostic dilemma isin differentiating pilomatrix carcinoma from the morecommon pilomatrixoma and certain forms of basaloidlesions, such as adenoid basal lesions found in the cervixuteri. These adenoid basal lesions show peripheral pal-isading, but without any stromal reaction and have nomalignant potential [8,9]. In the largest published seriesof pilomatrix carcinomas to date, Sau [10] et al. have dem-onstrated that pilomatrix carcinomas have a predilectionfor males and are commonly located on the head andneck. In their series of twenty patients, at least one died ofmetastatic disease.
Fayyazi and colleagues have assessed expression of the cellproliferation associated antigen Ki 67 (MIB1) in 15 pilo-matrixomas [11]. Histologically, four epthelial compo-nents within pilomatrixomas were distinguished,representing separate stages of tumour cell differentiation.The expression of Ki-67 was highest in the basalbasophilic cells of the epithelial compartments (> 70%cells) and was absent in the mesenchymal components.The expression of Ki-67 in greater than 50% of thebasaloid cells in our case, in combination with the localaggressiveness and the multiple recurrences makes thediagnosis of pilomatrix carcinoma.
ConclusionPilomatrix carcinomas are locally aggressive tumourswhich have a propensity for recurrence, especially whenincompletely excised. Wide excision is the preferred treat-ment and radiation therapy should be considered in thepresence of adverse features such as recurrent disease orresidual macroscopic disease, as in our case. In the caseswhere adjuvant chemotherapy and radiation have beenused there are instances of apparent cure with these as wellas cases with progression and death, despite treatment. Inrecurrent pilomatrix carcinoma, no chemotherapy regi-men has been demonstrated to provide local control or tohalt metastatic spread. The diagnosis should always beconsidered in the differential of any recurrent skin lesionwith locally invasive behaviour.
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ConsentWritten informed consent was obtained from the guardi-ans of the patient for publication of this Case Report andthe accompanying images. A copy of the written consentis available for review by the Editor-in-Chief of this jour-nal.
Competing interestsThe authors declare that they have no competing interests.
Authors' contributionsNA drafted and revised the manuscript, as well as com-pleting the literature search. DF supplied the clinicalinformation on the patient, and critically evaluated themanuscript. DG prepared all the pathological materialand revised the manuscript. JA devised the concept for themanuscript. All authors have read and approved the finalmanuscript.
MR features of intracranial pilomatrix carcinomaFigure 1MR features of intracranial pilomatrix carcinoma. Coronal T1 weighted image (post intravenous contrast) demonstrat-ing invasion of skull base with extension into intracranial cavity on left side from a large volume enhancing tumour mass arising from the cutaneous surface.
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Pilomatrix carcinomaFigure 2Pilomatrix carcinoma. The top panel (Fig. 2a) shows atypical basaloid epithelium with mitotic activity (H&E, × 400). The bottom panel (Fig. 2b) demonstrates high proliferative rate of basaloid epithelium on an MIB1 immunohistochemical stain (× 400).
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7. Green E, Sanusi D, Fowler MR: Pilomatrix carcinoma. J Am AcadDermatol 1987, 17:264-270.
8. DePond WD, Flauta VS, Lingamfelter DC, et al.: Adenoid basal car-cinoma of the cervix in a 20 year old female: a case report.Diagnostic Pathology 2006, 1:20.
9. Russell MJ, Fadare O: Adenoid basal lesions of the uterine cer-vix: evolving terminology and clinicopathological concepts.Diagnostic Pathology 2006, 1:18.
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