Pediatric Pathology and Molecular Medicine 19: 461-467, 2000Copyright © 2000 Taylor & Francis1522-7952/00 $12.00 + .00

FINE NEEDLE ASPIRATION CYTOLOGY OFPILOMATRICOMA: CASE REPORT AND REVIEW OFLITERATURE

Randall D. Craver. MOD Department if Pathology, Louisiana State UniuersiiyMedical School, New Orleans, Louisiana, USA

Evelyn Kluka. MOD Department if Otolaryngalogy, Louisiana State UnioersityMedical School, New Orleans, Louisiana, USA

Jane T. Lipscomb. MD D Department if Pathology, Louisiana State UnioersityMedical School, New Orleans, Louisiana, USA

D Pilomatricoma is a benign skin adnexal tumor that is underrecognized byfine needle aspirate, oftentimes resulting in an overdiagnosis qf malignancy. We present thefine needle aspirate qf a 7-month-oldchild with a pilomatricoma qf the cheek. The differential in this agegroup includes epidermal, dermoid,and branchial cleft cysts, thyroglossal duct remnants, granulomatous lymphadenitis, juvenile xanthogra­nuloma, and embryonal rhabdomyosarcoma. Recognition qf theghost cells and clinical correlation shouldallow accurate diagnosis qf this entity.

Keywords fine needle aspiration cytology, pediatric, pilomatricoma

Fine needle aspiration (FNA) continues to play an increasing role in assessinglumps and bumps in children. Pilomatricoma is a common benign skinadnexal (hair shaft) tumor, 60% of which occur within the first two decadesof life. Despite frequent reports describing the cytologic criteria, the correctdiagnosis by FNA of pilomatricoma has been made in only 51.3% (33 of 74)of reported cases in which FNA was obtained, and 53% (16 of 30) of similarcases reported in individuals less than 20 years of age. These statistics reflectaugmentation by a recent article in which 14 of 14 pilomatricomas werecorrectly diagnosed by FNA, otherwise the percentages would be 40% and44% [1].

We present the fine needle aspiration cytology of a pilomatricoma fromthe cheek of a 7-month-old child, review established cytologic criteria, anddiscuss the differential diagnosis in the pediatric age group.

Address correspondence to Randall D. Craver, MD, Laboratory, Children's Hospital, 200 HenryClay Ave., New Orleans, LA 70118, USA. E-mail: rdcraver@accesscom.net

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CASE REPORT

R. D. Craver et at.

This 7-rnonth-old Caucasian male child had multiple ear infectionsrequiring pressure equalizing tubes. A firm blue l-cm left cheek mass clini­cally thought to be a hemangioma had slowly enlarged over the previousseveral months. At the time of the bilateral pressure equalizing tube place­ment, a fine needle aspirate was obtained of the cheek mass. One week laterit was resected.

MATERIALS AND METHODS

A 23-gauge needle was used to obtain the aspirate. Air-dried smears andcytospin preparations were Wright stained. Alcohol fixed slides were Papani­colaou stained.

RESULTS

The fine needle aspiration was very cellular and polymorphous (FigureI). The predominant cell type was basaloid that occurred in large and smalltightly arranged clusters and as isolated cells. Most of these had scanty, pale,

FIGURE 1. The cellular smear with a "dirty" background is composed of cells found singly and inclusters. Ghost cells (upper center) and foreign body multinucleated giant cell (arrow) are evident.Nuclear fragility is demonstrated by the streaming artifact (Wright, 100 x).

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Pilomatricoma 463

FIGURE 2. Basaloid cell clusters with focal nuclear molding, prominent nucleoli, and some cellular disso­ciation (Wright, 400 x ),

or basophilic cytoplasm, and some lacked cytoplasm entirely. There was mildanisonucleosis, and the nuclear membranes were thin and uniform in thick­ness with smooth outlines. Nuclear chromatin was fine to coarsely granular,and evenly distributed. Nuclei had 1-3 prominent nucleoli, and there wasoccasional nuclear molding (Figure 2). Ghost cells occurred as large sheets ofblue non-nucleated cells on Wright-stained smears, and as clumps of refracti­le, orangeophilic keratin on the Pap stain (Figure 3). The background con­tained scattered multinucleated giant cells, granular debris, flecks of calcium,and a mixture of inflammatory cells. No mitoses were seen. Correlating thesecytologic features with the patient's age and lesion location led to a diagnosisof pilomatricoma. The histology from the resection 1 week later was typicalfor a pilomatricoma (Figure 4).

DISCUSSION

Criteria for the cytologic diagnosis of pilomatricomas are based onWoyke [2] and have been modified by Wong [3] and Solanki [4]. The mostimportant criterion is the ghost cell, most easily identified on the air-driedWright stain as clumps or single blue cells with central pallors where thenucleus should be [5, 6]. On Papanicolaou stain, these may appear as

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FIGURE 3. Comparison of ghost cells stained with Wright (A) and Papanicolaou (B), illustrates thatwhile easily identified with Wright stain, the cytologic detail of the ghost cells is less apparent on Papani­colaou. (A Wright, 400 X ; B Papanicolaou, 600 x ).

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FIGURE 4. Histologic section is typical for pilomatricoma with basaloid cells (closed curved arrow),ghost cells (open curved arrow), foreign body giant cells (closed arrow), and masses of keratin(Hematoxylin and eosin, 100 x ).

orangeophilic, amorphous material that may be ignored by the unwary asdebris [3J and when seen should prompt a careful search for the diagnosticghost cells. Basaloid cells are often found in clusters of varying size; haveround, vesicular, fine to coarsely granular, uniform to mildly variable nuclei[3J with smooth nuclear outlines; distinct nucleoli; scant cytoplasm; andmay show occasional mitoses without pallisading. Molding can occur but isnot prominent. These basaloid cells are more prominent in younger lesionsand become less conspicuous as the lesion matures [4]. Naked nuclei occursingly and in clusters [2]. The background is "dirty" [7J, with foreign bodygiant cells and calcified material.

The head and neck are frequent locations for pilomatricomas, where theymay present with a faceted stone texture under the skin or may have a bluishhue, clinically suggesting a hemangioma. They arise in Caucasians more fre­quently than blacks, may recur, and approximately 10% are multiple [8].There are occasional familial clusterings. Sarcoidosis, myotonic dystrophy,Gardner, Steinert, and Rubinstein-Taybi syndromes have associations withpilomatricomas [8, 9]. Pilomatrix carcinoma is rare, but it can occur as earlyas 8 years of age [I OJ and has arisen in the settings of recurrent pilomatri­coma [IIJ and multiple pilomatrixomas [12].

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466 R. D. Craver et al.

Suggestions for improving the 50% diagnostic accuracy so far reportedwith aspiration cytology of pilomatricomas include having the same individ­ual performing and interpreting the aspirates, using both alcohol-fixed,Papanicolaou-stained and air-dried, Romanovsky-stained specimens, andcareful clinical correlation keeping in mind that pilomatricoma is a muchmore frequent epithelial lesion in children than basal or squamous cell carcin­oma [13].

The following differential diagnoses should be considered in a FNA of ahead and neck lesion in childhood. Epidermal and dermoid cysts containpredominantly mature and anucleated squamous cells in the fine needle aspi­rate [3]. Epidermal cysts rarely undergo calcification [13]. Branchial cleftcysts and thyroglossal duct remnants may both contain anucleated andnucleated squames, ciliated columnar epithelial cells, and inflammatory cellsincluding foreign body giant cells if ruptured [14]. Papillary thyroid carcin­oma, found occasionally in the older child, is characterized by papillary ormonolayered clusters of epithelial cells and specific nuclear changes includingintranuclear inclusions and psammoma bodies.

Pilomatricomas are frequently mistaken for basal cell carcinomas, eventhough basal cell carcinomas are infrequent in the first two decades of life.Basal cell carcinomas have a distinct palisading pattern (absent inpilomatricomas), small indistinct nucleoli, no squamous differentiation [3, 7J,more nuclear atypia, and more irregularities in cell orientation and cell clus­ters [4]. Cohesiveness and lack of lymphoglandular bodies rule out a hema­togenous lesion [13J, although in areas, basaloid cells in pilomatricoma maybe dispersed as single cells, and the "dirty" background containing cell debrismay be confused with lymphoglandular bodies. Nuclei may be disruptedwhen smeared, further enhancing the similarity to a hematogenous lesion.Granulomatous lymphadenitis is characterized by lymphocytes, epitheloidhistiocytes, and lack of squamous cell [3]. Juvenile xanthogranulomas arecharacterized by histiocytes, Touton giant cells, a mixed inflammatory back­ground, and a lack of an epithelial component. Rhabdomyosarcomas(embryonal) are cellular, loosely cohesive with central or eccentric nuclei,finely granular chromatin, single small nucleoli, and scant cytoplasm. Rarely,strap cells with abundant dense eosinophilic cytoplasm may be present [14].

The most important clue in the diagnosis of pilomatricoma is the ghostcell, which occurs in few other lesions. One is the odontogenic ghost celltumor (OGCT)[15]. Cytologically, the OGCT may appear similar withbasaloid epithelial cells, ghost cells, multinucleate giant cells, and calcificdebris, but the OGCT also contains dentinoid material-ribbons of dense, hya­linized, acellular material, closely associated with basaloid cells. As theOGCT's location is usually the jaw, gingiva, or alveolar mucosa, separatingthis lesion from pilomatricoma should be easy on clinical grounds. Cranio­pharyngioma is another lesion with ghost cells.

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In many of the "earlier" lesions, the basaloid cells are prominent withless conspicuous ghost cells. However, with adequate sampling, careful searchfor ghost cells, and clinical correlation, FNA diagnosis of pilomatricoma canbe easily accomplished.

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3. Wong MP, Yuen ST, Collins RJ. Fine-needle aspiration biopsy of pilomatrix­oma: still a diagnostic trap for the unwary. Diagn Cytopathol 1994; 10:365-369.

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