Among sinonasal tumors, CDX-2 immunoexpression is not restricted to intestinal-type adenocarcinomas

SMARCB1/INI-1-Deficient sinonasal carcinoma demonstrates a poor prognosis but favorable clinical outcomes after PD-1/PD-L1 inhibitor therapy: A case series

Despite advances in multimodal cancer therapy, such as combining radical surgery with high-intensity chemoradiotherapy, for SMARCB1/INI-1-deficient sinonasal carcinoma (SDSC), the prognosis of patients remains poor. Immunotherapy is gaining increasing popularity as a novel treatment strategy for patients with SMARCB1/INI-1-deficient tumors. Herein, we report on the management of three patients with SDSC who received PD-1/PD-L1 inhibitor therapy as a part of multimodal therapy based on surgery and chemoradiotherapy. All three patients survived and demonstrated good clinical remission and disease control. To our knowledge, this is the first case series reporting the use of immunotherapy to improve clinical outcomes in neoadjuvant, adjuvant, and late first-line stages of treatment in patients with SDSC. Furthermore, we reviewed the relevant literature and further explored the correlation between SMARCB1/INI-1 deletion and immunotherapy.

Sinonasal Adenocarcinomas: An Update

Among sinonasal malignancies, adenocarcinomas account for the second most common entity after squamous cell carcinoma. They span a wide spectrum of neoplasms with heterogeneous features including intestinal-type adenocarcinoma (ITAC), non-intestinal-type adenocarcinomas (non-ITACs), and salivary-type adenocarcinomas. ITAC basically mirrors the histopathological aspects of gastrointestinal counterparts, showing variable tubulo-papillary, colonic, and mixed patterns with mucin production in 20% to 25% of cases. By contrast, non-ITACs do not show any differentiation toward intestinal or salivary phenotype, and they mainly represent a diagnosis of exclusion lacking a proper histopathological and molecular definition.

Tumors of the Nose and Paranasal Sinuses: Promoting Factors and Molecular Mechanisms-A Systematic Review

Sinonasal neoplasms are uncommon diseases, characterized by heterogeneous biological behavior, which frequently results in challenges in differential diagnosis and treatment choice. The aim of this review was to examine the pathogenesis and molecular mechanisms underlying the regulation of tumor initiation and growth, in order to better define diagnostic and therapeutic strategies as well as the prognostic impact of these rare neoplasms. A systematic review according to Preferred Reporting Items for Systematic Review and Meta-Analysis criteria was conducted between September and November 2022. The authors considered the three main histological patterns of sinonasal tumors, namely Squamous Cell Carcinoma, Intestinal-Type Adenocarcinoma, and Olfactory Neuroblastoma. In total, 246 articles were eventually included in the analysis. The genetic and epigenetic changes underlying the oncogenic process were discussed, through a qualitative synthesis of the included studies. The identification of a comprehensive model of carcinogenesis for each sinonasal cancer subtype is needed, in order to pave the way toward tailored treatment approaches and improve survival for this rare and challenging group of cancers.

Occurrence of Sinonasal Intestinal-Type Adenocarcinoma and Non-Intestinal-Type Adenocarcinoma in Two Countries with Different Patterns of Wood Dust Exposure

Sinonasal intestinal-type adenocarcinoma is strongly associated with hardwood dust exposure. Non-intestinal-type adenocarcinoma is a rarer and less well-known subtype considered not to be related with wood dust exposure. We determined the relative numbers of these two tumor types in 56 sinonasal adenocarcinoma patients in France and Finland, relating them with carefully assessed wood dust exposure histories. Diagnostic workup including immunohistochemistry for the intestinal markers CDX2 and CK20 indicated that the proportions of the two tumors differed significantly between France and Finland. In Finnish samples non-intestinal adenocarcinomas were more common than intestinal-type adenocarcinomas (12 non-intestinal vs. nine intestinal), while in the French samples the reverse was true (six non-intestinal vs. 29 intestinal). Such remarkably dissimilar occurrence of these tumors in France and Finland presumably reflects different pathogenetic circumstances in the two countries, and perhaps their different patterns of wood dust exposure. In France the main source of wood dust is from hardwoods. In Finland it is derived from softwoods. This is the first systematic comparison of the occurrence of intestinal-type adenocarcinoma and non-intestinal-type adenocarcinoma in two countries with different wood usage. It appears to be the first systematic study on differences in wood dust exposure between intestinal-type adenocarcinoma and non-intestinal-type adenocarcinoma.

Adenocarcinoma NOS arising from accessory lacrimal glands: A case report and a review of the literature

Primary malignant epithelial tumours arising from accessory lacrimal glands (ALGs) are extremely rare, with only few cases reported in literature. They generally appear as gradually increasing masses of the upper or the lower eyelid. Only one case of primary adenocarcinoma or adenocarcinoma not otherwise specified (ACNOS) from ALGs has been reported in literature. Herein, we describe a case of ACNOS arising from ALGs with an atypical clinical presentation and review prior cases of ALGs epithelial malignancies reported in the literature. A 78-year-old man referred to our Ocular Oncology Unit for adjuvant therapy after the excision of a conjunctival tumour of the left eye with a histological diagnosis of squamous cell carcinoma. He underwent topical chemotherapy with MMC and during follow up he presented a multinodular iris mass in his left eye. The MRI of the orbit showed an ocular mass infiltrating orbital soft tissues of the inferior palpebral region with an involvement of the corresponding zygomatic cutis. We performed orbital exenteration and histological studies revealed an epithelial neoplasm with a solido-glandular growth pattern with lumens containing an eosinophilic material positive for PAS and PAS-D. The immunohistochemical findings confirmed the diagnosis of adenocarcinoma NOS from ALGs. Although ALGs epithelial malignancies are extremely uncommon, they should be considered in the differential diagnosis of ocular tumours. A vigilant approach towards these entities is required, since they can be clinically insidious and locally aggressive.

Surgery as Single-Modality Treatment for Early-Stage Olfactory Neuroblastoma: An Institutional Experience, Systematic Review and Meta-analysis

BACKGROUND

For olfactory neuroblastoma (ONB), the combination of surgical tumor resection and radiation therapy (RT) has been considered the "gold standard" in treatment protocols intended to cure.

OBJECTIVE

To summarize evidence on the treatment of ONB using surgery alone.

METHODS

A retrospective institutional case series, a systematic review of the literature, and an individual patient data (IPD) meta-analysis on only surgically treated ONB patients.

RESULTS

At our institution, a total of 10 patients were treated through surgery alone and remained alive and free of disease at last follow-up. The IPD meta-analysis on 128 patients revealed a disease-free survival (DFS) and overall survival (OS) of 67.7% and 75.4% at 5 years and 57.1% and 71.9% at 10 years, respectively. Univariate analysis showed that Kadish stage C/D and Hyams grading III//IV significantly affected OS (P = 0.000 and P = 0.000) and DFS (P = 0.000 and P = 0.002). For low-risk patients, the DFS was 80.6% at 5 years and 67.8% at 10 years, respectively.

CONCLUSIONS

Surgery alone is an equivalent alternative to combined treatment in carefully selected low-risk ONB patients with better outcome measures than previously reported.

HER2 status in sinonasal intestinal-type adenocarcinoma

Given that the prognosis of patients with sinonasal intestinal-type adenocarcinoma (ITAC) has not significantly changed recently, there is a desire for new therapeutic approaches to improve clinical management. HER2-targeted therapy has remarkably improved the overall survival of patients with HER2 amplified tumors. To date, HER2 assessment has produced contradictory results in ITAC. The aim of this study was to assess HER2 status at both protein and DNA levels in a large series of ITAC. HER2 status was assessed by immunohistochemistry (IHC) and chromogenic in situ hybridization (CISH) in forty-three patients that underwent surgical resection for ITAC at the Otorhinolaryngology Section, Padua University Hospital, between 2007 and 2016. IHC was evaluated using the four-tier score developed for gastroesophageal cancer. As for IHC, 83.7% (36/43) of ITAC were scored 0, 14% (6/43) 1+, and 2.3% (1/43) 2+. No HER2 amplification was detected by CISH. The present is the largest study of sinonasal ITAC tested with both IHC and CISH confirmation for HER2 status. No HER2 overexpression/amplification was detected. Contrary to previous studies, our findings seem to rule out any oncogenetic role of HER2 in ITAC pathogenesis.

A case of nasal low-grade non-intestinal-type adenocarcinoma with aberrant CDX2 expression and a novel SYN2-PPARG gene fusion in a 13-year-old girl

We report the first patient (a 13-year-old girl) with a sinonasal low-grade non-intestinal-type adenocarcinoma showing aberrant CDX2 expression both within morular areas and in the tubular component and demonstrate for the first time a SYN2-PPARG gene fusion in this tumor type. The tumor arose from the nasal septum and had not spread beyond the nasal cavity.

Two Cases of Sinonasal Non-Intestinal-Type Adenocarcinoma with Squamoid Morules Expressing Nuclear β-Catenin and CDX2: A Curious Morphologic Finding Supported by Molecular Analysis

Sinonasal non-intestinal-type adenocarcinoma (non-ITAC) is a rare, morphologically diverse neoplasm of the head and neck. Squamoid morular metaplasia has recently been reported as an occasional finding in non-ITAC. Interestingly, these squamoid morules often show aberrant expression of CDX2 as well as nuclear expression of β-catenin, similar to other tumors that show this type of metaplasia, but the underlying mechanism responsible for this finding is not completely understood. We present two cases of low-grade non-ITAC with squamoid morules coexpressing CDX2 and nuclear β-catenin by immunohistochemistry, both of which were found to harbor a mutation in CTNNB1, the gene encoding β-catenin. This finding provides support that an alteration in the β-catenin pathway, including mutations in the β-catenin gene itself, is responsible for this recently described morphologic phenomenon in non-ITAC.

The Role of SATB2 as a Diagnostic Marker of Sinonasal Intestinal-type Adenocarcinoma

BACKGROUND

Intestinal-type adenocarcinoma (ITAC) of the nasal cavity and paranasal sinuses is an uncommon tumor associated with exposure to wood and leather dust, nickel, and possibly smoking. ITAC shares phenotypical features with colorectal carcinoma. In contrast to most non-intestinal-type sinonasal adenocarcinomas, ITAC is an aggressive adenocarcinoma with poor clinical outcome; therefore, its reliable separation from non-ITAC is very important.

AIM

The use of a combination of immunohistochemical markers of intestinal differentiation was tested in a cohort of sinonasal carcinomas of different types. The aim of this study was to explore a new intestinal marker, SATB2, in conjunction with CDX2 and CK20 in differential diagnosis of sinonasal adenocarcinomas.

MATERIALS AND METHODS

Seven ITACs, 66 non-ITACs, and 1 case of extensive intestinal metaplasia (IM) of the nasal mucosa were included in the study and stained with SATB2, CK20, CDX2, and CK7 antibodies. Detection of mismatch repair proteins was performed in all cases of ITAC. All 7 sinonasal ITACs have been tested for KRAS, NRAS, and BRAF gene mutations.

RESULTS

All ITACs showed positive expression for SATB2, whereas all non-ITAC cases were negative. The only 1 case of IM was found to be positive for SATB2, whereas the same case showed negative expression of CK20 and only focal immunostaining for CDX2. The genetic analysis showed that only 1 sinonasal ITAC (1/7) showed KRAS c.35G>C, p.(Gly12Ala) mutation, whereas BRAF and NRAS genes were wild type. Four ITACs revealed wild-type KRAS, NRAS, and BRAF, and 2 remaining cases were not analyzable. All ITACs showed preserved nuclear expression of mismatch repair proteins.

CONCLUSIONS

SATB2 in combination with CDX2 and CK20 differentiates sinonasal ITAC from non-ITAC with increased diagnostic sensitivity and specificity and detects IM in the sinonasal tract more easily.

Diagnosis of Multiple Primary Intestinal-Type Adenocarcinoma in the Lung by 18F-FDG PET/CT

A 74-year-old man with multiple soft tissue lesions in the lung, which were suspected to be metastatic neoplasms, underwent F-FDG PET/CT scan to detect primary malignancy. The images demonstrated that the lung and 2 retroperitoneal lymph nodes were the only affected organ or tissues with suspected primary lung neoplasms. Multiple intestinal-type adenocarcinoma was eventually diagnosed by CT-guided transthoracic needle aspiration biopsy.

Lateral Nasal Wall Respiratory Epithelial Adenomatoid Hamartoma (REAH): A Diagnostic Conundrum

INTRODUCTION

This study aims to report a rare case of a respiratory epithelial adenomatoid hamartoma (REAH) of the lateral nasal wall that had initially presented as a fungating mass, similar to that of a sinonasal malignancy, and its complete removal from the lateral nasal wall.

CASE REPORT

We report the case of a 58-year-old woman who presented to us with a chief complaint of recurrent right-sided epistaxis and nasal blockage for the past 4 months, which was progressively worsening. Histopathological examination confirmed the presence of a REAH instead of a sinonasal malignancy. The tumor was surgically excised from the lateral nasal wall using electrocautery under endoscopic guidance. The patient was then carefully followed-up after surgery, and the wound was successfully healed 3 months after the initial surgery. There was no evidence of recurrence 6 months after the initial surgery.

CONCLUSION

This case demonstrates the rare presentation of a REAH, which had arisen from the lateral nasal wall. Clinically, it is difficult to distinguish a REAH from a more notorious mass such as a sinonasal malignancy. Therefore, biopsy is mandatory in all cases of lateral nasal mass in order to rule out malignancy before confirming nasal REAH. Fortunately, as seen in this case, a lateral nasal REAH, once diagnosed, can be safely and easily removed from the lateral nasal wall using electrocautery with good surgical outcomes and a low rate of recurrence.

Primary intestinal-type adenocarcinoma of the buccal mucosa: A case report and literature review

Intestinal-type adenocarcinoma of the primary salivary glands is extremely rare. So far, only 11 cases of primary intestinal-type adenocarcinoma of the oral cavity and major salivary glands have been reported. Two of those tumors arose in the floor of mouth, 7 in the tongue, and 2 in the major salivary glands. However, it has remained unclear whether these tumors are derived from mature salivary glands, and primary intestinal-type adenocarcinoma of the buccal mucosa has not been reported previously. Here, we present the first documented case of primary intestinal-type adenocarcinoma arising in a minor salivary gland of the buccal mucosa. Histopathologically, the tumor resembled a well-differentiated or mucinous colonic adenocarcinoma. Immunohistochemically, the tumor cells were diffusely positive for AE1/AE3, CAM5.2, CK7, SATB2, β-catenin, p53, Ki-67, MUC2, and MUC5 AC. CK14 and CK20 were positive in some of the tumor cells. CDX2, CA19-9, SP-A, TTF-1, PSA, SMA, p63, and cyclin D1 were negative in the tumor cells. The tumor in the present case may have originated from salivary gland duct epithelium that underwent transformation to phenotypic intestinal-type epithelium. In this very rare case of primary intestinal-type adenocarcinoma of the buccal mucosa, we considered diagnostic markers that could be indicative of mature salivary gland origin.

Usefulness of NKX2.2 Immunohistochemistry for Distinguishing Ewing Sarcoma from Other Sinonasal Small Round Blue Cell Tumors

NKX2.2 is a new immunohistochemical marker that has been reported to be sensitive and specific for Ewing sarcoma (ES). It has not, however, been investigated specifically in the sinonasal small round blue cell tumor (SRBCT) differential diagnosis which includes many tumors specific to that site. It has also not been investigated in the newly recognized "adamantinoma-like" variant of ES. Immunohistochemistry for NKX2.2 was performed on 170 poorly differentiated sinonasal neoplasms: 73 squamous cell carcinomas (67 poorly differentiated, non-keratinizing, or basaloid types and 6 nasopharyngeal carcinomas), 46 olfactory neuroblastomas, 8 sinonasal undifferentiated carcinomas (SNUCs), 6 melanomas, 7 Ewing sarcomas, 6 SMARCB1-deficient carcinomas, 6 teratocarcinosarcomas, 5 alveolar rhabdomyosarcomas, 4 solid adenoid cystic carcinomas, 4 NK/T cell lymphomas, 3 NUT carcinomas, and 2 small cell carcinomas. NKX2.2 was positive in 7 of 7 (100%) Ewing sarcomas, including 3 adamantinoma-like variant (all diffuse, 5 strong and 2 weak). It was also positive in 5 of 6 (83%) teratocarcinosarcomas (strong, but focal), 12 of 46 (26%) olfactory neuroblastomas (diffuse, 2 strong and 10 weak), 4 of 6 melanomas (2 diffuse, 2 focal, all weak), and 1 of 2 small cell carcinomas (diffuse and strong). All squamous cell carcinomas, NUT carcinomas, SMARCB1-deficient carcinomas, SNUCs, solid adenoid cystic carcinomas, NK/T cell lymphomas, and alveolar rhabdomyosarcomas were negative. In the sinonasal SRBCT differential diagnosis, NKX2.2 is a useful and very sensitive marker for Ewing sarcoma, including the treacherous adamantinoma-like variant. At the same time, it is not entirely specific, as it will be positive in a subset of other neuroendocrine/neuroectodermal tumors. As a result, NKX2.2 must be utilized as part of an immunohistochemical panel with other markers, especially cytokeratins, melanoma markers, and CD99.

The Role of Targeted Therapy in the Management of Sinonasal Malignancies

Cancers develop secondary to genetic and epigenetic changes that provide the cell with a survival advantage that promotes cellular immortality. Malignancy arises when tumors use mechanisms to evade detection and destruction by the immune system. Many malignancies seem to elicit an immune response, yet somehow manage to avoid destruction by the cells of the immune system. Cancers may evade this immune response by numerous mechanisms. Several targeted immune therapies are available that block some of these inhibitory signals and enhance the cell-mediated immune response. Many of these agents hold significant promise for future treatment of sinonasal and ventral skull base malignancies.

Intestinal-Type Adenocarcinoma: Classification, Immunophenotype, Molecular Features and Differential Diagnosis

Intestinal-type adenocarcinoma is the second most frequent sinonasal adenocarcinoma. High incidence of these tumors is seen among workers with occupational wood dust exposure, particularly of hardwood dusts. Intestinal-type adenocarcinoma has striking histomorphologic and immunophenotypic similarities with colorectal adenocarcinomas, but on the level of molecular pathologic mechanisms these tumors have their own specific features different from gastrointestinal tumors. This article provides an update on current histopathologic classification of intestinal-type adenocarcinomas, their immunophenotypic properties, recent advances in molecular pathologic features and differential diagnostic considerations.

Primary Lingual Colonic-Type Adenocarcinoma: A Rare and Emerging Distinct Entity!

Primary colonic-type adenocarcinoma involving the tongue (CTAT) is exquisitely rare, with only four cases having been reported in the literature. We report the case of a 53-year-old woman with an anterior (oral) tongue mass. A review of literature was performed. Histomorphologic features were evaluated with standard hematoxylin and eosin stained sections. Ancillary testing was performed. The mass consisted of invasive adenocarcinoma associated with "dirty necrosis", akin to the phenotype seen in colorectal adenocarcinoma. By immunohistochemistry, the tumor cells were positive for AE1/3, CDX2, CK20, SATB2 and beta-catenin. This was initially felt to represent a metastatic colorectal adenocarcinoma but subsequent PET/CT and colonoscopy examination were negative for colorectal mass, excluding the possibility of a metastasis and confirming a diagnosis of CTAT. We raise awareness of the existence of this entity and recommend that metastatic disease be excluded before rendering a diagnosis of CTAT.

Clinical and morphological aspects of adenocarcinomas of the intestinal type in the inner nose: a retrospective multicenter analysis

Clinical and histological parameters from 117 patients with wood dust-related sinonasal adenocarcinomas of intestinal type (ITAC) were analyzed and correlated with a follow-up period of 5 years at least. The rate of survival for 5 years was 53.1 % and for 10 years 30.2 %. Only 33 patients were free of disease. 74.2 % of patients with recurrences died in relation to ITAC. As expected, tumors of T4-category had the worst prognosis. The mucus content of a tumor was the most important histological parameter. Endonasal methods of surgery had no more positive survival rates after 5 years. An effect of radiotherapy has to be in discussion. The high incidence of tumor recurrences requires control examinations consistently.

Sinonasal Adenocarcinoma: Update on Classification, Immunophenotype and Molecular Features

Adenocarcinomas of the sinonasal tract may originate from respiratory surface epithelium or the underlying seromucinous glands. These malignancies are divided into salivary-type adenocarcinomas and non-salivary-type adenocarcinomas. The latter are further divided into intestinal-type and nonintestinal-type adenocarcinomas. This review provides an update on tumor classification, differential diagnostic considerations and molecular features, as well as new adenocarcinoma entities in the sinonasal area.

Neuroendocrine tumours in rare sites: differences in nomenclature and diagnostics-a rare and ubiquitous histotype

The diagnosis of neuroendocrine tumours in typical sites, as gastrointestinal tract and lung, is based upon well-coded criteria that have become familiar to most of the pathologists. Much more difficult is the recognition and allocation of proper nomenclature to be referred to the same histotype in locations where these tumours have a lower incidence. The aim of our review was to provide a quick handbook of the main diagnostic pitfalls known in literature that can interpose in the histopathological examination of neuroendocrine tumours in rare sites (urinary system and male genital organs, female genital organs, head and neck and breast).

A Subset of Sinonasal Non-Intestinal Type Adenocarcinomas are Truly Seromucinous Adenocarcinomas: A Morphologic and Immunophenotypic Assessment and Description of a Novel Pitfall

While sinonasal intestinal type adenocarcinoma (ITAC) is defined by an intestinal phenotype, non-intestinal type adenocarcinoma (non-ITAC) is traditionally viewed as a diagnosis of exclusion, despite previous implication of a seromucinous phenotype and similarity to sinonasal seromucinous hamartomas (SSH). We performed a comparison of clinicopathologic and immunophenotypic features of ITAC, non-ITAC and SSH using traditional discriminatory markers and new markers of seromucinous differentiation. Twenty-three non-ITAC, 17 ITAC, and 5 SSH were retrieved (1987-2014). As expected, ITAC occurred predominantly in the nasal cavity in elderly patients (mean age 65 years) with a striking male predilection (15:2). Regardless of grade/subtype, all ITAC were invariably CK20 and CDX2 positive, and many (11/15) showed some CK7 positivity. Non-ITAC occurred in younger individuals (mean age 51 years) with a slight female predilection (male to female ratio: 10:13) and showed diverse morphologic patterns and grades, some with morphologic similarity to SSH. SSH occurred in younger individuals (mean age 33 years). Non-ITAC and SSH were invariably CK7 positive and CK20 negative, however, 4/22 non-ITAC and 2/5 SSH showed squamoid morular metaplasia that aberrantly expressed CDX2 and co-expressed nuclear β-catenin. Markers of seromucinous differentiation (S100, DOG1, and SOX10) were essentially absent in ITAC, but present to varying degrees in the majority of non-ITAC and all SSH. Thus, the term 'seromucinous adenocarcinoma' is the more appropriate designation for non-ITAC. Squamoid morules in non-ITAC and SSH may be an immunophenotypic pitfall given the aberrant CDX2 expression.

Utility of p40 in the Differential Diagnosis of Small Round Blue Cell Tumors of the Sinonasal Tract

The sinonasal tract may give rise to a broad range of neoplasms that share a "small round blue cell" tumor (SBRCT) appearance on routine histology, but treatment strategies depend on precise tumor classification. Immunohistochemistry for p63 is often employed in the sinonasal SRBCT differential diagnosis because it is highly sensitive for squamous cell carcinoma (SCC). However, p63 staining may be observed in other tumor types, a potential diagnostic pitfall. P40 is a more squamous-specific isoform of p63, and it may be more useful in distinguishing poorly differentiated SCC from its mimickers in the sinonasal tract. Immunohistochemistry for p40 and p63 was performed on 171 sinonasal neoplasms with SRBCT morphology: 73 SCCs (67 poorly differentiated, non-keratinizing, or basaloid types and 6 nasopharyngeal carcinomas), 46 esthesioneuroblastomas, 11 sinonasal undifferentiated carcinomas (SNUCs), 11 lymphomas, 9 melanomas, 7 alveolar rhabdomyosarcomas, 4 solid adenoid cystic carcinomas, 4 NUT midline carcinomas, 4 primitive neuroectodermal tumors (PNETs), and 2 small cell carcinomas. P40 was positive in 72 of 73 SCCs, and showed a diffuse distribution in all but one positive case. P40 immunoexpression was also observed in 13 of 46 (28 %) esthesioneuroblastomas, 6 of 11 (55 %) SNUCs, 2 of 4 (50 %) adenoid cystic carcinomas, 3 of 4 (75 %) NUT midline carcinomas, 1 of 2 (50 %) small cell carcinomas, and 1 of 4 (25 %) PNETs; in the non-SCC tumors, p40 staining was focal in most cases. P63 was positive in every p40-positive tumor. In addition, a p63+/p40- phenotype was seen 5 of 11 (45 %) lymphomas, 4 of 7 (57 %) alveolar rhabdomyosarcomas, 1 of 4 (25 %) PNETs, and 3 of 46 (7 %) esthesioneuroblastomas. All sinonasal melanomas were negative for both markers. In the sinonasal SRBCT differential diagnosis, both p40 and p63 are highly sensitive for SCC, but p40 is more specific. Notably, p40 is consistently negative in lymphomas and alveolar rhabdomyosarcomas, two tumors that are frequently p63-positive. It must be remembered, however, that even diffuse p40 immunostaining is not entirely specific for the squamous phenotype, and therefore it should be utilized as part of an immunohistochemical panel.